Understanding the welfare requirements of a neurologically and physically divergent captive male Sumatran orangutan (Pongo abelii)

1.1 Divergence and welfare

Humans responsible for the care of non-human animals (hereafter animals) have a responsibility to ensure that positive welfare is promoted in those individuals, and that they are free from harm. Over the past few decades, there has been a concerted effort to develop a system to measure wellbeing in captive animals. In the 1990s, the UK Farm Animal Welfare Council’s original ‘five freedoms’ of welfare (FAWC, 1992) were adapted by Mellor and Reid (1994) into a grading system known as the Five Domains Model. These overlapping domains are: 1) thirst, hunger, and malnutrition; 2) environmental challenge; 3) disease, injury, and functional impairment; 4) behavioural restriction; and 5) anxiety, fear, pain, and distress. Rather than measuring the presence or absence of each ‘freedom’, this system takes a more nuanced approach, acknowledging the degrees of compromise made in each of these areas of welfare, or ‘wellbeing’ (Mellor and Reid, 1994). The fifth domain, which relates to mental wellbeing, is a cumulative measure of the four physical domains, and therefore determines the overall score. The five domains were extended in 2015, with changes that included broadening the negative affective states with those related to an individual’s cognitive assessment of external circumstances, e.g. anxiety, fear, frustration, anger, helplessness, loneliness, and boredom (Mellor and Beausoleil, 2015). In addition, positive welfare states were taken into consideration. In the mental wellbeing domain, this includes states such as security, confidence, calmness, control, affectionate sociability, playfulness, and sexual gratification (Mellor and Beausoleil, 2015). These are related to behaviours encompassing agency, exercised through activities like environmental challenges, making choices, exploration, bonding with others, playing, and being able to retreat or defend oneself from attack. The latest iteration of the Five Domains Model incorporates both positive and negative human-animal interactions (Mellor et al., 2020).

Identifying the welfare needs of animals in captivity who diverge neurologically and/or physically from the species-typical ‘norm’ is a complicated issue, partly due to the individual nature of such conditions. Although there is variation within all species, some individuals are divergent to the extent that they experience life differently to others. This means that socio-environmental conditions which are deemed to meet welfare needs in most members of a species may not be able to meet the needs of all individuals. In humans, the 1975 declaration of the Union of the Physically Impaired Against Segregation marked a shift towards emphasising the constraints of external, socio-structural barriers preventing humans from fully participating in society, rather than disability being defined by individual, internal limitations (Edwards and Imrie, 2008). This is relevant for non-human animals in captivity, as there is potential for management changes and enclosure modifications to enable atypical individuals to lead a fulfilling life. However, the first step is to begin to understand the diversity of neurologically and physically atypical characteristics, and the extent to which captive environments can be adapted without compromising the welfare of other individuals.

Understanding of the needs of divergent animals is important in all captive contexts. However, for wild-born animals rescued from human-wildlife conflict and undergoing rehabilitation, there is an additional motivation. For example, orangutan (Pongo spp.) rehabilitation centres, which care for orangutans rescued from the illegal wildlife trade and other harmful situations, must make decisions on whether injured and otherwise atypical individuals can and should be released back into the wild or moved to semi-wild environments (Russon, 2008). If great apes are released into more natural environments, where individuals must be self-supporting, physical and cognitive impairments may result in difficulties such as obtaining food (Domain 1), building nests for resting safely (Domain 2), maintaining physical fitness and being able to reach and navigate the forest canopy (Domain 3), and defending against threats (Domain 4). All of these are likely to have a negative impact on mental wellbeing (Domain 5), leading to hunger, anxiety, fear, pain, and distress (Mellor et al., 2020). In some rehabilitation centres, chimpanzees (Pan troglodytes) with physical or psychological disabilities remain in enclosures rather than being released into partially free-range forested islands (Litchholt, 2021).

These careful management decisions made by rehabilitation centres will depend on the specific nature of an individual’s differences, whether physical or cognitive, and the extent to which they are likely to affect an individual’s ability to support themselves with a reasonable degree of wellbeing. There are complex ethical issues surrounding these decisions (see Palmer, 2018), particularly as it is difficult to predict the outcome of any release effort, and these risks must be balanced against potentially sub-optimal welfare in captivity. Although life in the wild is challenging for any individual, particularly those released from captivity, the challenge may be exacerbated for individuals with physical and/or cognitive differences. For example, severe physical injury can lower the dominance rank for chimpanzees and baboons (Papio cynocephalus) (e.g. Reynolds and Reynolds, 1965; Drews, 1996), indicating a reduction in competitive ability (Beamish and O’Riain, 2014).

1.2 Existing knowledge of divergent primates

There is poor knowledge of divergent individuals in animal research. There are some examples of studies with primates with physical impairments (Nakamichi, Fujii and Koyama, 1983; Cole, 1989; Hobaiter and Byrne, 2010; Antilla et al., 2013; Turner et al., 2014; Hopper, Shender and Ross, 2016; Matsumoto et al., 2016; Taylor, 2020), but few long-term studies (e.g. Sakuraba, Tomonaga and Hayashi, 2016), and limited research on the life history and development of atypical individuals, although there are some isolated examples (e.g. Savage and Snowdon, 1982; Hirata et al., 2017).

However, there are examples of divergent primates coping well in the wild. For example, a male free-ranging Japanese macaque (Macaca fuscata) called Tanago, who had missing hands and ‘distorted’ feet, was assessed during his first year of life and found to have impaired locomotion and social interactions (Nakamichi, Fujii and Koyama, 1983). Although Tanago’s physical impairments meant he struggled to keep up with other infants, leading to lower levels of play behaviours, Tanago was also less likely to receive aggression than other infants, and more likely to be groomed by other juveniles, usually females (Nakamichi, Fujii and Koyama, 1983). Tanago had a closer relationship with adults and female juveniles than other infant macaques, despite the rigid hierarchy in Japanese macaques which would normally have prevented him interacting with older troop members (Nakamichi, Fujii and Koyama, 1983). Therefore, Tanago generally adapted well to his physical impairments. As well as altering social interactions, physical impairments can also influence the length of time atypical individuals spend in different activities. For example, activities like locomotion may be more tiring with a physical impairment. In a long-term study of free-ranging Japanese macaques, disabled females spent more time resting and less time socialising than nondisabled females (Turner et al., 2014). However, as with Tanago, this was not due to social alienation, as disabled females received less aggression, and their groom solicitations were as successful as nondisabled females (Turner et al., 2014). Another study showed similar increased resting time for disabled baboons, but no changes in grooming or social vigilance behaviours (Beamish and O’Riain, 2014). Physical divergence does not necessarily prevent wild animals from living a long and fulfilling life. A wild female Japanese macaque called Mozu, whose hands and feet had an abnormal morphology (possibly from pesticide pollution), became a prominent troop member, living for 28 years and rearing five offspring (Cole, 1989, in Taylor, 2020).

1.3 Benefits of research

In captive contexts where long-term care is being provided, there are several key motivations for understanding divergent individuals. The first is that understanding the needs of these individuals is fundamental to promoting their welfare. As there is currently limited research in this area, sharing knowledge about specific cases can help caretakers know what to expect, particularly during an individual’s development. By understanding of how the needs of atypical individuals can be fulfilled in relation to the Five Domains Model, a knowledge base can be established which caretakers can use to guide individual care and husbandry to optimise the quality of life for atypical individuals. Not only does this have clear benefits for animal welfare, but there are also financial implications for the zoo. Atypical individuals whose needs are not being met may exhibit behaviours related to negative affect, e.g. anger and frustration. As well as having the potential to negatively affect visitor perceptions, such behaviours could be destructive and costly and could even put the wellbeing of other individuals in the group at risk. Additional keeper time may be required to manage and care for some individuals with cognitive impairments, e.g. where there are difficulties training an animal to move to a specific area of the enclosure to enable cleaning. An inability to socially coexist with other conspecifics could mean complicated housing arrangements, and additional space requirements to avoid conflict. Therefore, when the needs of atypical individuals are understood and being met, there is likely to be less pressure on the workload of caretakers and less financial pressure on the zoo.

Research involving atypical animals can also contribute to improved wellbeing for the individuals themselves, as taking part in research can be enriching. There can be both cognitive and physical benefits from taking part in research. For example, cognitive enrichment was used for rehabilitating movement in an adult male chimpanzee (Pan troglodytes) called Reo, who experienced acute transverse myelitis at the age of 24 which resulted in impaired walking ability (Sakuraba, Tomonaga and Hayashi, 2016). Reo was provided with a puzzle task linked to a feeder two meters away, designed to encourage Reo to walk between the puzzle and the feeder. This led to an increased total travel distance from 136.7 meters to 506.3 meters within a ten-day period, and an increase in percentage of walking during the study sessions from 1.2% to 27.2%. In addition, research can help to identify the skill levels of an individual, which can lead to the development of targeted interventions (e.g. Ernst et al., 2005) with ongoing benefits beyond the scope of the study. However, determining an appropriate level of challenge depends on the individual abilities of each animal (Meehan and Mench, 2007), which may be particularly difficult to determine for divergent individuals. Therefore, case studies which involve appropriately tailored enrichment devices could be used as an important point of reference.

In order to address the gap in research on individuals with unique welfare needs, a case study was carried out on an adult male Sumatran orangutan (Pongo abelii), Jiwa, who is cognitively and physically divergent from other orangutans. The aim of this study was to evaluate areas of the Five Domains Model where Jiwa’s differences may be associated with an impact on wellbeing; and to determine an appropriate difficult level of cognitive enrichment for Jiwa, to aid in tailoring future enrichment to his individual needs.

2.1 Subject and housing

The research subject, Jiwa, was born in Jersey Zoo and at the time of the study had been living there for his whole life. He was housed during the day in a group with another female orangutan and her son, who was his half-brother. There was another enclosure adjacent to Jiwa’s group, which included his father, and another mother-infant dyad. Both groups could see and hear each other. There was no immersive physical contact between the two groups, although limited tactile contact was possible through the metal mesh partition. At the time of the study, a lar gibbon (Hylobates lar) also had regular access to the orangutan enclosures. All orangutans had access to indoor and outdoor areas. Jiwa was fed separately from the other members of his group, in an off-show bed den, which was where the experiment took place, and this is where he was housed overnight.

2.2 Life history and development

There were two main sources of information on Jiwa’s development. The first was his full daily keeper records from 17/10/1999 (his birth) to 07/02/2022, obtained through his specimen report on the Zoological Information Management System (ZIMS). The second was an unpublished internal report that summarised Jiwa’s development during his first year of life. This was written by a keeper, Rupert Beck, on 22/10/2000. These documents were scrutinised for indications of Jiwa’s developmental milestones, which were then compared with expected milestones for wild (van Noordwijk and van Schaik, 2005; van Noordwijk et al., 2009) and/or captive (Lethmate, 1977a, 1977b; Miller and Nadler, 1981; Beck, 2000; Nakamichi, 2004) orangutans. These milestones were: first break in continuous body contact with his mother, first time being carried by an individual other than his mother (captivity only), first time supporting his body weight on the barwork of the enclosure (captivity only), first independent locomotion from his mother, first attempt at nest-building, first locomotion more than 10 metres away from his mother, first attempt at using tools, first attempt at making tools, and being fully weaned.

Although wild Sumatran orangutans as young as three may be able to build arboreal nests adequate for a brief rest (van Noordwijk et al., 2009), fully functional nest-building is rarely possible in the zoo environment due to a lack of appropriate base structures and limited nesting materials (Chappell and Thorpe, 2022). Therefore, only the first attempt at ‘practising’ nest building (van Noordwijk et al., 2009), i.e. arranging nesting materials without building an adequate nest for sleeping, was included as a milestone. The milestone for the first attempt at using tools encompasses tools discarded by mother or peers (van Noordwijk and van Schaik, 2005). Milestones which are not normally possible within the zoo context were excluded, e.g. travelling more than 50 meters away from the mother. Milestones based on activity budgets were also excluded, due to lack of comparative data in the keeper reports.

In addition to developmental milestones, physical measurements of Jiwa’s growth were compared with expected rates for a male Sumatran orangutan. These included body weight in kilograms and age of deciduous (‘baby teeth’) dental emergence (Beck, 2000; Fooden & Izor, 1983). Male orangutans are known to demonstrate distinctive bimaturism, with secondary sexual characteristics developing at very different ages and, in some individuals, taking as long as 30 years to develop (Utami et al., 2002). However, there is very little data available for the weight of unflanged male orangutans, since in captivity males nearly always develop flanges (Pradhan, van Noordwijk and van Schaik, 2012). Therefore, as Bornean and Sumatran orangutans are considered to be approximately the same size (Smith and Jungers, 1997), the comparative data includes a range of different sources, including captive (Fooden and Izor, 1983) and wild-born (Markham and Groves, 1990; Smith and Jungers, 1997) Sumatran orangutans, wild-born Bornean orangutans living in rehabilitation centres with no flanges or developing flanges (Prasetyo, 2019), and unflanged orangutan skeletal data (species unknown) (Kralick et al., 2023).

2.3 Adaptation of cognitive enrichment

The second part of the study took place from 17th January to 5th March 2022 at Jersey Zoo and involved tailoring a cognitive enrichment device to a suitable level for Jiwa. This involved a probe feeder apparatus which had been previously presented to Jiwa’s peers (see Bridgeland-Stephens et al., in preparation). This was constructed from a 50 cm length of 5 cm diameter hollow plastic pipe with a food reward inside (see Figure 1). The food reward was initially peanut butter, but this was changed to porridge from session 3 onwards, as Jiwa’s preferred food type and therefore a greater incentive.

Figure 1. Research apparatus used in session 1, which was suspended from the ceiling from the two cords and orientated with the end of the tube facing Jiwa.

A food reward was inside the tube which could only be reached using a stick.

The study methods were adapted on a weekly basis according to Jiwa’s success at reaching the food reward, and the contents of each session are shown in Table 1. Each session lasted 30 minutes and was filmed using two ‘APEMAN’ A77 video cameras, one on a tripod and the other clipped to the front of the researcher. In the first session, the tube was suspended from the ceiling using 15 cm lengths of 4 mm nylon cord. The cords were attached 5 cm from each end of the tube using M8 eye bolts that were screwed into pipe clips clamped around the pipe. At the ceiling end, the cord was tied to carabiners, which hung from eye hooks in wooden batons that were fixed to the ceiling outside the enclosure. In the first session, the tube was suspended outside the enclosure, 25 cm away from the wire mesh, so that the food reward could only be reached using a stick. The intention was that, if Jiwa was successful, the apparatus would be gradually increased in difficulty by moving the cords closer together until Jiwa was no longer to access the food reward, which would provide an indication of Jiwa’s skill level. However, as Jiwa did not use a tool to access the food reward when the apparatus was hung outside the enclosure, out of reach of his hands (session one), the difficulty of the enrichment was lowered to a very basic level.

When given the tube part of the apparatus loose inside his enclosure, Jiwa obtained the food reward when within reach of his fingers (session two), but not when the peanut butter was out of reach (20 cm from either end of the tube), even while the researcher was conducting a social learning demonstration using a second tube outside the enclosure and vocalising to draw Jiwa’s attention (sessions three and four). The subsequent four sessions (sessions five to eight) were bi-weekly and required Jiwa to remove the stick (already touching the food reward) while the apparatus was being held outside the enclosure by the researcher. As Jiwa did participate in this form of enrichment, the difficulty level was increased in the final session (session nine) by providing Jiwa a stick, to see whether he would insert this into the apparatus himself to obtain the food reward.

The full details of the social demonstration procedure can be found in Table 2. The first five sessions took place weekly (17th January until 14th February), and the last four sessions took place biweekly (21st February to 5th March). Ethical approval for this research was obtained from the University of Birmingham Animal Welfare and Ethical Review Body (ERN_19-1935) and the Durrell Wildlife Conservation Trust Ethics Committee (ETH21/2019). The dataset for this article is available on an online repository (Bridgeland-Stephens, 2023).

3.1 Birth and physical development

Jiwa was born in 1999 at Jersey Zoo (UK) and was 23 years old at the time of the study. Although the cause of Jiwa’s atypical development is unknown, Beck (2000) considered the possibility that excessive lip and face sucking behaviour from his mother resulted in a lack of sufficient nutrition and oxygen. However, it is also possible that Jiwa was deprived of oxygen prior to birth, e.g. due to complications with the umbilical cord or function of the placenta, and that his mother’s behaviour was in reaction to Jiwa’s lack of response. Although this behaviour was stopped through keeper intervention with negative reinforcement (water jets), for the following five months “Jiwa appeared to be in a semi vegetative state … giving the impression that he was temporarily brain damaged” (Beck, 2000).

Figure 2 shows Jiwa’s growth rate compared with the expected growth rate of male orangutans with flanges, males developing flanges, and unflanged males (Fooden and Izor, 1983; Prasetyo, 2019; Kralick et al., 2023). On average, captive orangutans are 80% heavier than their wild counterparts (Fooden and Izor, 1983). Jiwa’s weight, last measured in 2001 as 36.8 kg, sits just below the expected range for unflanged males, although it should be noted that both his mother and grandmother were smaller than average in size (Beck, 2000; Fooden & Izor, 1983), weighing 42 kg and 40 kg in adulthood respectively (Deputy Head of Mammals at Jersey Zoo, Gordon Hunt, personal communication).

Figure 2. Jiwa’s growth in body weight compared to expected growth in flanged males where species is unknown (Fooden & Izor, 1983), wild-born Bornean (Pongo pygmaeus) males in rehabilitation centres with developing flanges or no flanges (Prasetyo, 2019), wild Sumatran (Pongo abelii) males with unknown flange status (Markham & Groves, 1990; Smith & Jungers, 1997), and data based on unflanged male orangutan skeletons where species and exact age is not specified (Kralick et al., 2023). For the skeletal data, exact age was not specified, and so subjects characterised as ‘young adult’ and ‘adult’ by Kralick et al. (2023) were recorded here as 10 years and 18 years, respectively.

Expected dental emergence rates for orangutans in captivity can be seen in Figure 3, showing that the eruption of Jiwa’s deciduous teeth generally appears to have taken place later than, or at the late end of, expected ranges of dental emergence reported by Beck (2000) and Fooden and Izor (1983). The exception to this is with his upper lateral incisors, which erupted well within the expected age range of 6.5-13 months for male Sumatran orangutans (Fooden and Izor, 1983). It appears that Jiwa’s teeth emerged within a three-month period, contradicting the expected staggered dental emergence (see Figure 3). There was no available data for the eruption of Jiwa’s canines or secondary premolars. There was also insufficient data to compare the eruption of Jiwa’s permanent (adult) teeth with expected emergence rates, although he was observed to have a possible full set of permanent mandible teeth by eight and a half years old (recorded on 07/06/2008 in the keepers’ contemporaneous notes).

Figure 3. Jiwa’s deciduous dental emergence compared with expected rates. Black dots indicate time Jiwa’s dental eruptions are first observed by keepers, either in the keeper records or as reported by Beck (2000). Expected milestone ranges (rounded to the nearest half-month) reported by Fooden and Izor (1983) are indicated by the upper pink bars; the lower blue bars indicate ranges reported by Beck (2000). The dental emergence of Jiwa’s peers at Jersey Zoo is mixed-sex and based on four individuals for lower incisor emergence, and two individuals for all other dental eruptions (Beck, 2000).

In addition to Jiwa’s small size, his physical abilities were also impaired at some points in his development. Jiwa was described as being noticeably weak from 11 weeks old, with an insufficient grip that necessitated bodily support from his mother; when this did not take place, Jiwa fell on a number of occasions (Beck, 2000). However, at seven months old, a physical examination found that Jiwa “appeared perfectly healthy with normal audio and visual responses, normal heartbeat, good grip/overall strength, and normal blood count and chemistry” (Beck, 2000).

Orangutan infants would normally be expected to explore away from their mothers, but in very close proximity to them, from around six months old (Gordon Hunt, personal communication). However, Jiwa’s first observed independent locomotion occurred at one year old (milestone four). This involved climbing one foot up the barwork, during which the keeper noted that Jiwa was “still quite slow and shaky” (30/10/2000). A few months later, at 15 months, Jiwa was still unable to walk quadrupedally (26/02/2001), although he started crawling across the floor at 21 months “with his hands holding each other, and pushing himself with his back legs” (13/07/2001). Elsewhere, he was described as crawling as if he was “climbing on a flat surface” (05/09/2001). Despite his difficulty with moving across the floor, as well as finding “smooth right-angle ledges” particularly challenging (08/11/2001), Jiwa’s climbing skills improved considerably during this period (14/08/2001; 22/12/2001). At just over two years old, Jiwa was observed standing bipedally for the first time, using a rope to steady himself (17/11/2001). At around two and a half years old, keepers noted a concern with Jiwa not clinging properly ventro-ventrally and was either having to be supported by his mother’s arm, or carried ventro-dorsally, on his mother’s shoulders (18/04/2002). Approaching three years of age, Jiwa was described as being “confident and competent” walking quadrupedally outside, relatively competent walking quadrupedally inside, with his mobility and arm/leg strength having noticeably improved over the preceding few months (04/09/2002). Although Jiwa was at this point capable of walking “more normally” quadrupedally on the indoor floor, he was still often seen “moving along the floor as though he is swimming” (11/04/2003). This was partially attributed to the ‘slippery’ floor surface (i.e. smooth and flat) and was seen to improve when Jiwa was moving through deep litter, giving him more grip and therefore the opportunity to build strength in his legs (15/01/2004). A photo of Jiwa at around this age is shown in Figure 4.

Figure 4. Jiwa (right) at four years old with mother Mawar (left).

Photo credit: Gregory Guida, 2004.

By five years old, Jiwa’s quadrupedal walking and bipedal standing had noticeably improved, and “his overall movement continues to improve gradually” (16/10/2004). However, even today, Jiwa’s style of locomotion is visibly distinctive compared to his peers (personal observation). For example, when walking quadrupedally, Jiwa’s right shoulder is often hunched; he lands heavily on his limbs and walks with his arms out to the side (rather than in front) of his body, possibly for greater stability. In addition, Jiwa generally moves more slowly than his peers.

In summary, Jiwa is a particularly small orangutan, even for an unflanged male. His deciduous dental emergence generally took place later than expected, with some exceptions, and occurred within a three-month period, rather than the expected staggered dental emergence rates. Early in life, Jiwa was physically weak, with some difficulty locomoting, and his first independent locomotion took place six months later than expected, at one years old. Jiwa experienced considerably difficulty with quadrupedal walking in his early years, and, even now, continues to have a distinctive and slow locomotion style.

3.2 Developmental milestones

The expected developmental milestones for wild and captive orangutans (where available) are shown in Figure 5. Although Jiwa’s first break in body contact with his mother was observed around the expected time of one to three months (milestone one), he reached the next two milestones somewhat later. Jiwa was not observed being carried by an individual other than his mother (milestone two) until seven months old (31/05/2000), four months later than other infants born at Jersey zoo (Beck, 2000). However, this would not have been possible for the first five months, as Jiwa and his mother were restricted to a separate part of the enclosure for observational purposes, away from the main group (Beck, 2000). As the initial instance of Jiwa breaking body contact was of Jiwa transitioning from his mother to his grandmother, it is not clear whether Jiwa was taken against his mother’s will. However, Beck (2000) indicates that it would not have been surprising for Jiwa to have been given up voluntarily to his grandmother, due to the close familial relationship. Although Jiwa moved from his mother to the barwork in a stationary position (milestone three) at a later point than the expected range of two to four months, at 11 months old (25/09/2000), Jiwa was observed moving independently soon afterwards (30/10/2000), at an early point within the expected range of one to two years. However, Jiwa’s first attempt at nestbuilding (milestone five) was considerably delayed beyond the expected one to two years.

Figure 5. Jiwa’s development of independence compared with expected rates. Black dots indicate time Jiwa’s milestones are first observed by keepers. Expected milestones (rounded to the nearest half-month) for wild orangutans are indicated by the upper pink bars and are based on van Noordwijk & van Schaik (2005) and van Noordwijk et al. (2009). Expected milestones for captive orangutans are indicated by the lower blue bares, and are based on Lethmate (1977a, 1977b), Miller & Nadler (1981), Miles (1990), Beck (2000), and Nakamichi (2004). Jiwa’s data for the weaning milestone indicates the earliest possible data Jiwa could have been weaned (23/07/2004).

The first observed instance of Jiwa being more than 10 metres in distance from his mother (milestone six) occurred when a conspecific stole Jiwa and carried him inside while his mother remained outside, presumed to be unaware of the incident (26/03/2002). Jiwa’s first intentional distancing from his mother may take place much later, but is not detailed in the keeper records. The exact time of weaning (milestone seven) is unclear; it is likely to have taken place at some point between four years and nine months (when the keepers become doubtful of Jiwa’s mother’s milk production) (23/07/2004) and the point at which Jiwa’s younger brother was born, at five years seven months (24/05/2005). Not long after this, Jiwa initiated spending the night apart from his mother and seven-week-old brother (milestone eight), by refusing to enter the back den with them (11/07/2005). Approximately one year after Jiwa started sleeping alone, he was observed sleeping at the far end of the outside island, which is as far away as possible in the orangutan enclosure at Jersey Zoo (11/08/2006).

3.3 Sexual development

Jiwa’s first recorded mating attempt occurred at just over five and a half years old and was with his mother (21/05/2005). Some secondary sexual characteristics started to emerge at just over eight years old, with a small ‘beard’ (03/12/2007). Soon afterwards, keepers started to encourage him to regularly sleep alone as “he is now maturing” (17/03/2008). The next notable change occurred at just over fourteen years old, after a nine-year-old male conspecific, Jaya (born 13/05/04), left the zoo (14/11/2013). Six weeks later, the keepers observed that “Jiwa’s locomotion and co-ordination seem to have improved markedly; he has shown increased facial development: widening of his face, with cheek pads emerging, and his libido (has) rapidly developed” (25/12/2013). Soon after this, Jiwa’s frequent - and sometimes physically rough - sexual attention towards conspecifics became problematic, and he was put on a one-off, six-week course of cyproterone acetate to reduce testosterone levels and manage his libido (04/02/2014). Five months later, Jiwa was castrated (24/07/2014).

It is not until over four years later, at the age of eighteen, that Jiwa’s repertoire of vocalisations changed to emulate typical mating calls, with one display-like instance of “a deep guttural vocalisation building up higher in short bursts”, and a few months later “almost producing a long call” (17/05/2018; 01/10/2018). Jiwa’s long call seemed to mature over the next year and was “almost a proper call” by 20 years old (18/11/2019). However, despite some development of secondary sexual characteristics, Jiwa was physically very different from his flanged father, Dagu, and had not yet developed full cheek pads or a throat sac (see Figure 6).

Figure 6. Comparison of cheek pad development between Jiwa aged 21 (left) and his dominant male father Dagu (right).

Photo credit: Jersey Zoo.

3.4 Cognitive abilities

Jiwa’s cognitive differences were apparent from a young age. At nine months old, keepers noted that Jiwa “shows little or no obvious behavioural development. Appears to only react to objects that are within 6 inches of his face, though he appears fine in every other respect” (08/07/2000). 52 days later, Jiwa began interacting with the keeper (29/08/2000) and with other objects, such as a sunflower leaf and stem (11/09/2000), and a piece of bamboo (15/09/2000). However, at one year old, Jiwa was described as being “to all intents and purposes a 3-4 month old infant” (Beck, 2000). When introduced to glass at nearly two and a half years old, Jiwa “(looks) a little confused when touching the glass, trying to work out why he could not touch (the) keeper behind it” (10/02/2002). However, the keeper noted here that Jiwa responded well to his own name at this stage, as well as visual cues. Around this time, Jiwa was observed to be “increasingly playful and confident, especially when not mixed with other orangs” (03/04/2002). Approaching three years old, Jiwa was recognising familiar people, and showing interest and curiosity toward unfamiliar people, demonstrating that he could tell them apart (10/07/2002). After Jiwa’s younger brother was born, the keepers noted difficulty with Jiwa understanding routines without the direction of his mother: “Jiwa does not appreciate the necessity to move to different parts of the enclosure during routines” (25/05/2005). However, Jiwa appeared to settle into a routine fairly easily after this (18/06/2005).

Jiwa displayed some possible nest-building behaviour (milestone five) with wood wool and a paper bag in the nest basket at nearly three and a half years old (17/11/2002), well beyond the expected one to two years (see Figure 5). The next mention of nesting behaviour was five years later, at nearly eight and a half years old although, from the casual tone of the keeper’s note (“Jiwa … made his nest in there”), this does not appear to be the first time Jiwa was seen nest-building (21/02/2008).

By five years old, tool use is not uncommon in orangutans, and is seen at a younger age in both captivity and in the wild (Galdikas, 1982; Miles, 1990; Nakamichi, 2004). Although Jiwa has been seen by keepers to pick up extractive tools dropped by others, he has never been observed to use a tool to dip for food rewards (Gordon Hunt, personal communication). However, there were some instances where Jiwa used simple tools, i.e. knocking down a thermometer using a piece of bamboo at 20 years old (07/04/2020). Later in the same year, it was noted that “Jiwa (was) very alert and interactive with (the) Keeper this morning, more so than Keeper … has ever seen before, his movements were quick, he made eye contact several times” (11/10/2020).

3.5 Cognitive enrichment

During the nine experimental sessions, Jiwa did not use a tool to access the food reward, whether the apparatus was hanging outside the enclosure, being held by the researcher outside the enclosure, or loose inside the enclosure. However, Jiwa did access the food reward by withdrawing sticks that were placed inside the tube by the researcher. In addition, over the four sessions which involved this activity, Jiwa was consistently successful and showed a marked improvement over time in the number of sticks he withdrew per session (see Figure 7). This is despite several occasions when Jiwa because frustrated, evidenced by repeated ‘distress’ vocalisations (Gordon Hunt, personal communication). Jiwa’s performance can be contrasted with the other orangutans at Jersey Zoo, all of whom attempted to use a tool to obtain the food reward when the apparatus was hanging outside the enclosure (Bridgeland-Stephens et al., in preparation). Although Dagu did not obtain the food reward at any point in a five-week period, the females and infants successfully retrieved the food reward in the first session.

Figure 7. Number of stick removals per session.

Sessions 5 to 8 involved Jiwa withdrawing sticks that were already placed inside the apparatus. Note: Session 2 did not involve sticks.

4.1 Study limitations

There are several limitations with the fact that nearly all information regarding Jiwa was obtained from keeper records and a single report made when Jiwa was one years old. The first is that the keeper records compile observations from several different keepers, who may have interpreted Jiwa’s behaviour in different ways over the two-decade time period. The second limitation is that keepers are not able to continually observe the animals in their care, so first observations of a particular behaviour may not reflect the first occurrence of that behaviour. Lastly, as the study was carried out in hindsight, not all developmental milestones have been recorded for Jiwa. For example, although Jiwa’s initial nest-building behaviour was recorded, there is no further mention of his full nest-building behaviour until years later. Despite these limitations, valuable insights can be drawn about Jiwa’s development and ability.

4.2 Notable differences in development

Jiwa reached many developmental milestones at an expected rate: the first break in body contact with his mother, first independent locomotion, first instance of being more than 10 metres away from his mother, and the first night spent apart from his mother. Although some of these milestones were not initiated by Jiwa himself, for example being taken by a conspecific and moved 10 metres away from his mother, others were. For example, Jiwa himself initiated spending the night apart from his mother for the first time when his younger brother was seven weeks old. There are other instances where Jiwa exercised agency and independence, for example spending the night at the far end of the outside enclosure when he was approaching seven years old.

However, there were also several key differences between Jiwa and other orangutans, particularly in his cognitive development, which appears to have been noticeably slow. Jiwa’s first observed attempt at nest building does not take place until nearly three and a half years old, considerably longer than the expected age of one to two years for both wild and captive Sumatran orangutans (Lethmate, 1977a; van Noordwijk et al., 2009). It was not possible to determine Jiwa’s nest-building ability from the keeper records. Nest building in the wild is more cognitively demanding than in captivity (van Casteren et al., 2012), but even in captive environments great apes can employ varying levels of complexity (Videan, 2006). However, it is likely that Jiwa and his peers would not have had the opportunity to learn more complex nest-building techniques, such as bending and weaving (Videan, 2006), as the main nesting material provided to the orangutans was wood wool. As well as the delay in nest-building behaviours, Jiwa had not yet learned how to use extractive tools, unlike his peers. However, he was observed to use a simple form of tool, i.e. knocking down a thermometer using a bamboo stick at around 20 years old.

Jiwa is also physically atypical, with an unusually low weight, generally late deciduous dental eruptions, some difficulty with locomotion, and only ‘half-developed’ secondary sexual characteristics. Thompson et al. (2012) found that male orangutans (Pongo spp.) with noticeable changes in their secondary sexual characteristics before 14 years old had higher levels of testosterone as adults than those who completed their development from 14 onwards. Although Jiwa’s testosterone levels are not specified in the keeper records, Jiwa comfortably fits into the latter category, as his facial structure widened and cheek pads started to emerge a couple of months after his 14th birthday. In addition, within the following year, Jiwa received a six-week course of a testosterone-lowering medication and was subsequently castrated. This is likely to be a contributing factor to Jiwa having not yet developed full flanges at 24 years old, in addition to the presence of his flanged father in the adjacent enclosure. However, although secondary sexual characteristics are also thought to be delayed by the presence of a dominant male (Maggioncalda, 1995), most males in captivity usually do develop these characteristics, even in the presence of another flanged male (Pradhan, van Noordwijk and van Schaik, 2012). Therefore, it seems more likely in this case that the medical interventions had a greater restrictive effect on the development of Jiwa’s secondary sexual characteristics than the presence of his father.

The physical and cognitive differences seen in Jiwa are reminiscent of a 1982 case study of two Bornean orangutan twins, with the second born infant suspected to have perinatal hypoxia (oxygen deficiency during birth) (Savage and Snowdon, 1982). Both orangutans were tested at around six years of age, with the second born orangutan exhibiting physical and cognitive differences to her brother. Physical differences included less frequent brachiation and more clumsy and uncoordinated locomotion, with an inability to perform fine motor movements (Savage and Snowdon, 1982). Cognitive differences included deficiencies in learning and short-term memory, and an inability to use tools (Savage and Snowdon, 1982). Although Jiwa was not assessed using the same battery of tests as in this study, it is possible that he was similarly deprived of oxygen, either during birth, or due to his mother’s unusual face- and lip-sucking behaviour immediately afterwards.

4.3 Implications for wellbeing

Regarding the Five Domains Model, it seems likely that Jiwa’s nutritional and environmental needs are largely unaffected by his condition. The keeper records do not mention difficulties with Jiwa’s food or water intake. The only environmental constraint which may have affected Jiwa and his mother was during Jiwa’s first five months of life, when the mother-infant dyad was kept in the back dens for close observation. Although this may not have been ideal, it was a justifiable - and arguably necessary - intervention due to the concerns regarding Jiwa’s survival and wellbeing at the start of his life. As an adult, Jiwa’s wellbeing is affected in the ‘health’ domain, with a particularly low body weight, low levels of strength, and functional impairments in locomotion. Although Jiwa is able to access the same areas in the enclosure as the other orangutans, it would not be surprising if locomotion in general was more physically demanding for him than for his peers. There may also be more complex locomotion behaviours that Jiwa has not been able to acquire. It would be interesting to conduct a study on activity budgets of Jiwa and his peers, to see whether Jiwa spends more time resting than the other orangutans (e.g. Beamish and O’Riain, 2014; Turner et al., 2014) to compensate for his physical impairments.

It is somewhat difficult to determine how Jiwa’s differences may affect his wellbeing in the fourth domain, which relates to the exercise of agency. Although Jiwa has access to the same enrichment programme as the other orangutans at Jersey Zoo, his impaired cognitive ability means that is not able to use some forms of enrichment which are accessible to his peers, e.g. extractive foraging. This may be detrimental to his ability to express agency and exercise control over the environment. Regarding social interactions, Jiwa generally appears to have a positive relationship with his peers (Gordon Hunt, personal communication). Although Jiwa has had the opportunity to engage in sexual activity, which is a form of agency, his attention towards his peers was so frequent - and sometimes rough - that it was deemed problematic. As a result, Jiwa was given a libedo-reducing medication to resolve this. Although Jiwa’s sexual agency was curbed by this medication, there was a trade-off involved, as this intervention arguably improved the wellbeing of Jiwa’s peers, who were sometimes distressed by his mating attempts.

It is not possible to know the extent to which Jiwa’s mental state was affected by the limitations in the physical/functional domains of welfare described above. However, there are several areas which have the potential to result in a negative affective state. For example, it is possible that Jiwa’s physical difficulties lead at times to pain, weakness, or physical exhaustion. Regarding limitations to his agency, Jiwa may experience frustration or helplessness, e.g. when faced with cognitive enrichment he is unable to use. It is possible that he has experienced sexual frustration, although this is likely to have been tempered by his medication. However, in general, Jiwa does not appear to be a particularly anxious individual, and seems relatively secure, with positive social relationships and the opportunity to play with younger conspecifics (Gordon Hunt, personal communication). Therefore, despite the potential impairments to Jiwa’s wellbeing, it seems that he is still able to live a fulfilling and well-rounded life.

4.4 Benefits of enrichment

Although Jiwa did not use tools to obtain the food reward within the assessment period, unlike most of his peers, he did show a marked improvement in the number of sticks he withdrew from the apparatus over the four sessions that involved this activity. This improvement occurred despite the frustration Jiwa appeared to exhibit on several occasions. Jiwa’s increased frequency in withdrawing sticks not only indicates continuing engagement in the activity, but also suggests that Jiwa learned how to use this version of the enrichment, evidenced by his increase success at the task over time. These results suggest that the activity was successfully tailored to Jiwa’s abilities, which is an important requirement when providing captive animals with cognitive enrichment (Meehan and Mench, 2007; Clark, 2011). Jiwa’s participation in this activity is connected with a number of areas of wellbeing, but the most relevant is the opportunity to express agency. By exercising control over his environment, despite the challenge and initial stress involved, Jiwa managed to obtain a food reward. Reward is linked to a number of benefits, including enhanced learning, positive affect, and motivation (Berridge and Robinson, 2003). In turn, agency, effective problem-solving, self-motivation, and positive affect are all aspects of psychological resilience, or the ability to ‘bounce back’ from stress (Mandleco and Peery, 2000; Isen, 2001; Rutter, 2012; Hornor, 2017). Therefore, ongoing participation in cognitive enrichment of this kind may have some very real, long-term benefits for Jiwa’s welfare. In future, this device could be adapted by building a permanent tube into the side of Jiwa’s enclosure, where keepers can place food rewards and sticks in advance, so that Jiwa can use the enrichment by himself without being supervised or encouraged.

4.5 Implications for animal management

Jiwa’s differences raise a number of considerations for animal management. At the beginning of Jiwa’s life, his behavioural differences and the concerns about his mother’s maternal behaviour raised challenges for the zoo. These included additional keeper time, general psychological stress that may have been experienced by the keepers due to anxiety about Jiwa’s welfare (e.g. Jensvold, 2022; Marino, 2023), and the financial impact of additional medical requirements relating to Jiwa’s care, i.e. the course of medication to limit his libido. Even now, there are some challenges posed by Jiwa’s needs, for example the fact that he is unable to participate in extractive foraging enrichment, which is regularly provided to the orangutans at Jersey Zoo (Gordon Hunt, personal communication). Although this study shows how cognitive enrichment can be tailored to meet Jiwa’s needs, it should be noted that this process took four and a half hours over a period of five weeks; as keeper time is limited, this may not always be logistically possible to achieve. However, despite these challenges, Jiwa’s conditions have been successfully managed by the zoo, to the extent that Jiwa has managed to develop independence, functional social relationships, and is strong and skilled enough to freely move around the enclosure. As well as benefiting Jiwa’s wellbeing, this is logistically beneficial for the zoo, as it reduces the level of resources required to care for Jiwa.

Ethical considerations

This research took place as part of the normal husbandry schedule for orangutans at Jersey Zoo, and participation in the research was entirely voluntary for the subject animal. One session was terminated when the subject became mildly frustrated after seeing another orangutan eating food within his line of vision. In all subsequent sessions, food was provided to the subject prior to the research taking place to avoid this scenario. All research sessions took place under the supervision of a keeper and would have been terminated if the subject animal had exhibited any signs of stress.