A survey of abnormal repetitive behaviors in North American river otters housed in zoos

Stereotypic behaviors, indicating poor welfare and studied in a variety of species (especially carnivores), appear related to characteristics of current and past environments. Although North American river otters (Lontra canadensis) often develop abnormal, repetitive, possibly stereotypic behaviors, no published reports describe otter housing and management or characterize how these variables relate to abnormal repetitive behavior (ARB) occurrence. The first author developed surveys to gather data on housing, individual history, management, and the prevalence of ARBs in otters housed in facilities accredited by the Association of Zoos and Aquariums. Consistent with anecdotal evidence that otters are prone to ARBs, 46% of river otters in the study exhibit them. ARBs were mostly locomotor and often preceded feeding. Exhibits where otters were fed and trained housed a greater percentage of nonhuman animals with ARBs. This study supports the Tarou, Bloomsmith, and Maple (2005) report that more hands-on management is associated with higher levels of ARBs because management efforts are only for animals with ARBs. Escape motivation, breeding season, feeding cues, and ability to forage may affect ARBs in river otters and should be investigated.     

Risk Factors and Remediation of Self-Injurious and Self-Abuse Behavior in Rhesus Macaques

Considered signs of decreased welfare—abnormal behaviors such as self-injury and self-abuse among nonhuman primates housed in the laboratory—may put into question the validity and reliability of scientific research using these animals as models. Providing environmental enrichment decreases the incidence of some undesirable behaviors but is often unsuccessful at ameliorating the most severe types of abnormal behaviors. To prevent such behaviors from developing, it is important to identify risk factors that provide insight into the causes of certain abnormal behaviors. This study confirmed previous research identifying nursery rearing, single housing, and time spent in single housing as important risk factors. Results also indicate that the number of cage relocations affects the development of these behaviors. In addition, this study presents new data on comorbidity of several abnormal behaviors and discusses possible reasons for these patterns.     

Using Fecal Glucocorticoids to Assess Stress Levels in Captive River Otters

Abstract Reintroduction projects often expose animals to a series of acute stressors that may cause chronic stress and lead to the stress response. The stress response results in the release of glucocorticoids that, when excessive, can cause detrimental effects to the animal. Glucocorticoids can be extracted from feces and quantified as an effective method for assessing stress levels. We collected scats from 10 river otters (Lontra canadensis; 3 from MD and 7 from NY, USA) held captive for the Pennsylvania River Otter Reintroduction Project (PRORP). We used these scats to verify the use of the Correlate-EIA^TM Corticosterone Enzyme Immunoassay Kit (Assay Designs, Inc., Ann Arbor, MI) to evaluate stress levels in otters. We also determined trends in stress levels during the initial 10–12 days otters were in PRORP captivity, and compared glucocorticoid levels for 5 of the New York otters the morning before, the morning of, and the morning after veterinary examinations to determine if associated procedures (e.g., physical and chemical restraint) caused increased stress levels. Glucocorticoid concentrations declined from time 1 to time 2 for the 3 otters from Maryland (an average decline of about 6-fold) and for 5 of 7 otters from New York. Among otters evaluated for stress associated with veterinary examinations, average glucocorticoid concentrations were increased the morning of and the morning after veterinary examinations from the day before the veterinary examinations. We demonstrated that fecal glucocorticoids are an effective method for assessing stress levels in otters and that PRORP's captive management program did not contribute to increasing stress during the 10–12-day evaluation period. Fecal glucocorticoid assays could be used to evaluate stress levels of zoo or permanently captive otters, determine the most effective husbandry techniques for housing otters, and evaluate effects of both management practices and environmental conditions in the wild and in captivity.     

Stereotypies and other abnormal repetitive behaviors: potential impact on validity, reliability, and replicability of scientific outcomes

Normal behavior plays a key role in facilitating homeostasis, especially by allowing the animal to control and modify its environment. Captive environments may interfere with these behavioral responses, and the resulting stress may alter many physiological parameters. Abnormal behaviors indicate that an animal is unable to adjust behaviorally to the captive environment and, hence, may be expressing abnormal physiology. Therefore, captive environments may affect the following aspects of an experiment: validity, by introducing abnormal animals into experiments; reliability, by increasing interindividual variation through the introduction of such individuals; and replicability, by altering the number and type of such individuals between laboratories. Thus, far from increasing variability, enrichment may actually improve validity, reliability, and replicability by reducing the number of abnormal animals introduced into experiments. In this article, the specific example of abnormal repetitive behaviors (ARBs) is explored. ARBs in captive animals appear to involve the same mechanisms as ARBs in human psychiatry, which reflect underlying abnormalities of brain function. ARBs are also correlated with a wide range of behavioral changes that affect experimental outcomes. Thus, ARBs in laboratory animals may compromise validity, reliability, and replicability, especially in behavioral experiments; and enrichments that prevent ARB may enhance validity, reliability, and replicability. Although many links in this argument have been tested experimentally, key issues still remain in the interpretation of these data. In particular, it is currently unclear (1) whether or not the differences in brain function seen in animals performing ARB are abnormal, (2) which common behavioral paradigms are affected by ARB, and (3) whether enrichment does indeed improve the quality of behavioral data. Ongoing and future work addressing these issues is outlined.     

Factors affecting reproduction in zoo‐housed geoffroy's tamarins(Saguinus geoffroyi)

The captive population of Geoffroy's tamarins (Saguinus geoffroyi) has suffered a severe decline over the past 10 years. This population decline is attributed not to a failure to produce offspring, but rather to a failure to successfully rear offspring. To date, no studies have quantitatively examined the behaviors and hormones of this tamarin species in captivity. Therefore, this study was conducted to determine whether there were any discernable factors that could be correlated with failure to rear offspring in S. geoffroyi. Fifteen adult Geoffroy's tamarins (GTs) at the Cleveland Metroparks Zoo (CMZ) were observed by means of instantaneous sampling on a focal animal. In addition, all instances of social behaviors were recorded. A factorial arrangement of treatments was used, as animals were divided between a colony‐housing situation and a non‐colony situation with hand‐reared and mother‐reared animals in both treatments. Repeated‐measures analysis of variance (ANOVA) showed no interactions between the treatments, and no differences between rearing histories for the behaviors studied. However, animals housed in a colony setting exhibited higher levels of aggressive behaviors and lower activity levels compared to those in a non‐colony setting. There also was a trend for colony‐housed animals to huddle, scent‐mark, and exhibit sexual behaviors more often than non‐colony animals. First‐morning‐void urine samples were collected once per week, and assays for E₁C and PdG indicated that reproduction was not being suppressed. ANOVA conducted on samples assayed for excreted cortisol showed no differences in mean cortisol concentration by rearing histories or housing conditions. While these physiological indicators reveal no signs of stress, high levels of aggressive and territorial behaviors indicate social unrest in the colony‐housed condition, which may be contributing to the poor reproductive success of those individuals. Zoo Biol 22:545–559, 2003. © 2003 Wiley‐Liss, Inc.     

Why and how should we use environmental enrichment to tackle stereotypic behaviour?

This paper summarises recent findings on the causation of stereotypic behaviours and other abnormal repetitive behaviours (ARBs) in captive animals: primarily motivational frustration and/or brain dysfunction, with possible contributory roles also being played by habit-formation and ‘coping’ effects. We then review the extent to which ARBs occur in zoos and similar, estimating that at least 10 000 captive wild animals are affected worldwide. We argue for ‘zero tolerance’ of such ARBs, because stress and poor welfare raise ethical issues, while abnormal behavioural phenotypes and possibilities of impaired brain development challenge both the indirect (e.g. educational) and the direct, intrinsic conservation value of affected animals. We then consider five potential means by which ARBs may be tackled: genetic selection; pharmacological treatment; the reinforcement of alternative behaviours; punishment; and environmental enrichment. All except punishment have potentially useful roles to play, but enrichment is the preferred approach: it is most likely to tackle the problems underlying stereotypic behaviours, and thence to improve both welfare and behaviour with few unwanted side-effects. Nevertheless, in zoos, environmental enrichment to date has only had partial success, with no study managing to abolish ARBs in all its subjects—suggesting either that the enrichments currently being used are never quite optimal, or that by the time they are tackled, ARBs have become resistant to change. We suggest some ways in which the effectiveness of enrichments may be enhanced; propose that certain properties of ARBs may usefully help evaluate their likely ‘treatability’; and emphasise that if improving welfare is more important than just reducing ARB, then additional measures are needed in order to first, reliably identify those individuals most at risk from poor welfare, and then, to fully evaluate the welfare impact of enrichments. This paper also emphasises, with examples, the enormous potential value of zoo-derived data for helping understand how taxon, ecological niche, rearing history, and current housing together affect animals’ responses to captivity.     

Effects of social and inanimate enrichment on the behavior of yearling rhesus monkeys

Certain types of inanimate environmental enrichment have been shown to positively affect the behavior of laboratory primates, as has housing them in appropriate social conditions. While social housing is generally advocated as an important environmental enhancement, few studies have attempted to measure the influence of social conditions on the effects of inanimate enrichment or to compare the relative merits of social and inanimate enhancements. In the present study, inanimate enrichment (predominately physical and feeding enhancements) resulted in increased species-typical behavior for socially restricted subjects. However, social enrichment (living in groups) appeared to be more beneficial for young rhesus monkeys, leading to increased species-typical activities and decreased abnormal activities. The behavior of one cohort of yearling rhesus monkeys (Macaca mulatta) housed in small peer groups was compared with the behavior of four yearling cohorts housed in single cages. Half the animals in each cohort received a three-phase enrichment program and the rest served as controls. Group-housed yearlings spent significantly more time feeding and exploring and significantly less time behaving abnormally, self-grooming, and drinking than did singly housed yearlings. Enriched subjects spent significantly more time playing by themselves, and significantly less time self-grooming and exploring than did controls. Among group-housed subjects only, there were no differences between enriched and control monkeys. Captive primates should be housed socially, whenever appropriate, as the first and most important step in an enrichment program, with the provision of inanimate enhancements being considerably less important. Limited resources for inanimate enrichment programs instead should be focused on those individuals who can not be housed socially. © 1996 Wiley-Liss, Inc.     

Preliminary Findings of Fecal Gonadal Hormone Concentrations in Six Captive Sea Otters (Enhydra lutris) after Deslorelin Implantation

The sea otter (Enhydra lutris) is a popular exhibit animal in many zoos and aquariums worldwide. Captive sea otters from these populations are owned by the United States Fish and Wildlife Service (USFWS). The USFWS has requested that these sea otters be prevented from breeding in order to save captive space for wild rescued animals. Sea otters are often housed in mixed sex groups, therefore a chemical contraceptive method or surgical removal of gonads must be used to prevent potential pregnancy. The contraceptive, Suprelorin® or deslorelin, has been used in many different species to effectively suppress reproduction but duration of effect may vary not only between species but also individuals. Here, we report the effects of one to several consecutive deslorelin implants on gonadal reproductive hormones found in fecal samples from six captive sea otters (two males and four females) compared to two control otters (one male and one female) housed at three zoological institutions. We documented the longitudinal hormone signatures of many stages of the contraceptive cycle including pretreatment (PT), stimulatory phase (S), effective contraception (EC), and hormone reversal (HR) that was characterized by a return to normal hormone levels. Deslorelin was found to be an effective contraceptive in sea otters and was found to be reversible documented by a live birth following treatment, however the duration of suppression in females was much longer than expected with a 6‐month and a 1‐year implant lasting between 3 and 4 years in females. Zoo Biol. 32:307–315, 2013. © 2012 Wiley Periodicals, Inc.     

Stereotypic and self-injurious behavior in rhesus macaques: a survey and retrospective analysis of environment and early experience

Abnormal behavior in captive rhesus monkeys can range from active whole-body and self-directed stereotypies to self-injurious behavior (SIB). Although abnormal behaviors are common in singly-housed rhesus monkeys, the type and frequency of these behaviors are highly variable across individual animals, and the factors influencing them are equally varied. The purpose of this investigation was to survey abnormal behavior in a large population of rhesus macaques, to characterize the relationship between stereotypies and self-injury, and to identify potential risk factors for these aberrant behaviors. Behavioral assessments of 362 individually housed rhesus monkeys were collected at the New England Regional Primate Research Center (NERPRC) and combined with colony records. Of the 362 animals surveyed, 321 exhibited at least one abnormal behavior (mean: 2.3, range: 1-8). The most common behavior was pacing. Sex differences were apparent, with males showing more abnormal behavior than females. SIB was also associated with stereotypies. Animals with a veterinary record of self-injury exhibited a greater number of self-directed stereotypies than those that did not self-injure. Housing and protocol conditions, such as individual housing at an early age, longer time housed individually, greater number of blood draws, and nursery rearing, were shown to be risk factors for abnormal behavior. Thus, many factors may influence the development and maintenance of abnormal behavior in captive primates. Some of these factors are intrinsic to the individual (e.g., sex effects), whereas others are related to colony management practices, rearing conditions, and research protocols.     

Single- or Pair-Housed: Which Is Better for Captive Southern Tamanduas?

The captive environment can limit some important behavioral options for nonhuman animals, which often results in decreased welfare. The companion of a conspecific can be a source of complexity in captivity, but this aspect has received little attention for solitary species. This study investigated the effects of two different housing conditions on the behavior of a solitary species, the Southern tamandua (Tamandua tetradactyla). Six individuals housed singly and four housed in pairs in two Brazilian zoological institutions were observed for 10 days from 09:00h to 17:00h during the rainy season. Each individual was observed for 26:40 hours. Compared with singly housed tamanduas, paired animals were less inactive (single = 74.62 ± 5.2%, paired = 28.51 ± 0.04% of the records), foraged and explored more (single = 11.07 ± 3.0%, paired 31.48 ± 0.01% of the records), and exhibited a diversity of behaviors 102.56% greater than single tamanduas. These results suggest that interactions with conspecifics in captivity, even for solitary animals, can promote the performance of desirable behaviors, which in several species has been correlated with improved welfare.     

The efficacy of diazepam treatment for the management of acute wounding episodes in captive rhesus macaques

The spontaneous development of self-injurious behavior (SIB) in singly housed monkeys poses a challenge for their management and well-being in captivity. Relatively little information is available on effective treatments for SIB. This study examined the effects of diazepam (Valium) on self-wounding and other abnormal behaviors in eight individually housed male rhesus monkeys (Macaca mulatta). Each monkey's response to an anxiolytic dose of diazepam (1 mg/kg or greater orally) was compared with the animal's behavior during drug-free periods. When examined across all animals, treatment with diazepam did not significantly alter wounding frequency or rates of self-directed biting without wounding. However, closer examination of the data revealed that four of the animals showed significant decreases in self-biting and wounding frequency (positive responders, PR group), whereas the remaining monkeys showed a trend towards increased wounding frequency (negative responders, NR group). Subsequent examination of colony and veterinary records demonstrated that compared with NR monkeys, PR monkeys had spent significantly more years in individual cage housing and had experienced a greater number of minor veterinary procedures. PR animals also were significantly less likely to have a documented history of self-biting behavior. Our findings suggest that SIB is not a homogeneous disorder in rhesus monkeys; rather, distinct subtypes exist that require different treatment approaches.     

Pair Housing for Female Longtailed and Rhesus Macaques in the Laboratory: Behavior in Protected Contact Versus Full Contact

Pair housing for caged macaques in the laboratory generally allows unrestricted tactile contact but, less commonly, may involve limited contact via grooming-contact bars or perforated panels. The purpose of using this protected contact housing, which prevents entry into pair-mates' cages, typically is to accommodate research and management requirements. The study used behavioral data collected on 12 pairs of female longtailed macaques (Macaca fascicularis) at the Washington National Primate Research Center and 7 pairs of female rhesus macaques (Macaca mulatta) housed at the Tulane National Primate Research Center to assess the relative benefits of protected versus full protected contact. The study collected data in stable pairs housed first in protected contact followed by full contact. Species combined, the study found the presence of the panel was associated with lower levels of social grooming and higher levels of self-grooming, abnormal behavior, and tension-related behavior. Within species, only the protected- versus full-contact contrasts for abnormal and tension were statistically significant—and only for rhesus macaques. Results suggest that for female rhesus macaques, potential disadvantages or inconveniences of full contact should be balanced against the improved behavioral profile in comparison to protected contact. The use of protected contact among female longtailed macaques does not appear to require the same cost-benefit analysis.     

Hand‐rearing and rehabilitation of orphaned wild giant otters,Pteronura brasiliensis,on the Rupununi river,Guyana, South America

From 1985–2003, 34 orphaned giant otters, Pteronura brasiliensis, (22 males, 12 females) were hand raised for eventual return to the wild at The Karanambu Cattle Company Limited Ranch (Karanambu), on the Rupununi River, Guyana, South America. The orphans ranged in age from 2 weeks to 9 months old; most were 8–10‐week‐old cubs. Feeding, housing, exercising, veterinary care, and rehabilitation protocols for young giant otters were developed during this period. Six cubs died during hand‐rearing; of these, four died from illness or injury, and two were killed, one by a caiman and one by another orphaned otter. Of 34 giant otters brought to Karanambu, 28 (82%) were reared successfully to an age and condition suitable for rehabilitation, and 18 (53%) returned to the wild. Ten otters survived hand‐rearing but died either before or during the process of rehabilitation. These hand‐reared giant otters were killed by people (3 known, 2 presumed) or other giant otters (5), including one male otter that remained at Karanambu for several years. During rehabilitation, young giant otters chose to spend increasing amounts of time on the Rupununi River away from human care, often interacting with wild giant otters. Although long‐term monitoring was not possible, Karanambu staff observed most (15 of 18) of the rehabilitated otters repeatedly, for as long as 4 years after their return to the river. The giant otter rehabilitation program at Karanambu generated new knowledge about this species, and offered visitors the opportunity to observe them. Zoo Biol 24:153–167, 2005. © 2005 Wiley‐Liss, Inc.     

Does human proximity affect antibody prevalence in marine-foraging river otters (Lontra canadensis)?

The investigation of diseases of free-ranging river otters (Lontra canadensis) is a primary conservation priority for this species; however, very little is known about diseases of river otters that forage in marine environments. To identify and better understand pathogens that could be important to marine-foraging river otters, other wildlife species, domestic animals, and humans and to determine if proximity to human population could be a factor in disease exposure, serum samples from 55 free-ranging marine-foraging river otters were tested for antibodies to selected pathogens. Thirty-five animals were captured in Prince William Sound, Alaska (USA), an area of low human density, and 20 were captured in the San Juan Islands, Washington State (USA), an area characterized by higher human density. Of 40 river otters tested by indirect immunofluorescent antibody test, 17.5% were seropositive (titer > or =320) for Toxoplasma gondii. All positive animals came from Washington. Of 35 river otters tested for antibodies to Leptospira interrogans using the microscopic agglutination test, 10 of 20 (50%) from Washington were seropositive (titer > or =200). None of the 15 tested animals from Alaska were positive. Antibodies to Neospora caninum (n=40), Sarcocystis neurona (n=40), Brucella abortus (n=55), avian influenza (n=40), canine distemper virus (n=55), phocine distemper virus (n=55), dolphin morbillivirus (n=55), porpoise morbillivirus (n=55), and Aleutian disease parvovirus (n=46) were not detected. Identifying exposure to T. gondii and L. interrogans in otters from Washington State but not in otters from Alaska suggests that living proximal to higher human density and its associated agricultural activities, domestic animals, and rodent populations could enhance river otter exposure to these pathogens.     

Preliminary investigation of social interactions and feeding behavior in captive group-housed Tasmanian devils (Sarcophilus Harrisii)

As the number of Tasmanian devils (Sarcophilus harrisii) in captivity increases, an understanding of captive social dynamics and behavior is becoming increasingly important. In the wild, devils are solitary, although sometimes, they congregate to feed on a large carcass. However, it is common to house devils in groups as a form of social enrichment. This study investigated how behavior at feeding time of captive Tasmanian devils varied in groups of different sizes. Observations were made of individually housed devils and devils in groups of two, three, five, and six, when presented with a carcass on which to feed. Total feeding duration ranged from 6.5 to 47.4 minutes per observation period (70 minutes). There was no significant interaction between feeding duration and group size during the experiment. Feeding duration varied daily and depended on carcass size. Social housing of Tasmanian devils enabled them to display dyadic and agonistic behaviors during feeding. Observing behaviors and learning from the outcomes of these interactions can improve husbandry techniques. Creating a captive environment that encourages natural behaviors may enhance survival in the wild following translocation.     

Seasonal shifts in giant panda feeding behavior: relationships to bamboo plant part consumption

The giant panda (Ailuropoda melanoleuca) is classified as a carnivore, yet subsists on a diet comprised almost exclusively of bamboo. Wild and captive giant pandas use highly selective foraging behaviors for processing and consuming bamboo. These behaviors are for the first time quantified in captive giant pandas over a 5‐year period of time showing highly specific seasonal trends. Giant panda feeding behavior was recorded using live video observations of two giant pandas housed at the Memphis Zoo from November 2003 to June 2008. Leaf was the primary plant part consumed from June to December, whereas culm was consumed primarily from February to May, with both bears displaying similar seasonal shifts in plant part consumption. From May to June, leaf consumption increased significantly (P‐values<0.001); from June to August, leaf consumption remained high and stable. From December to March, leaf consumption decreased significantly (P‐values<0.001). Specific behaviors for bamboo leaf and culm consumption were also observed. Both bears formed wads of leaves before ingestion while feeding on leaf, but the male employed this feeding behavior more often than the female (54 and 33%, respectively). Both bears used similar culm‐stripping behavior (26 and 25%), used to remove the outer layer and isolate the pith for consumption. This study indicates that unique seasonal foraging behaviors observed in wild pandas are also apparent in captive animals in relation to plant part selectivity and feeding behaviors. Zoo Biol 29:470–483, 2010. © 2009 Wiley‐Liss, Inc.     

Commensal association of the common kingfisher with foraging Eurasian otters

Positive interactions between birds and mammals are a fascinating aspect of animal behaviour. Feeding associations may consist of local enhancement or facilitation, and in the latter case, of commensalism or mutualism depending on the benefits received by the facilitator. We report here on a previously undescribed feeding association between piscivorous birds and Eurasian otters Lutra lutra. In Spain, common kingfisher Alcedo atthis and grey heron Ardea cinerea were observed closely following foraging otters and benefited from feeding opportunities provided by these. Behavioural observations of otters in central Spain (28.4 hr; 19 days) revealed that an association with kingfishers occurred in 33% of otter foraging events (n = 92). Simultaneous observations in northern Spain (14.2 hr; 16 days) showed an association between otters and kingfishers or grey herons in 41.6% and 11.7% of otter foraging events (n = 77), respectively. The association probability between kingfishers and otters increased significantly when otters foraged closer to the shore and on small fish rather than other prey (crayfish or large fish). Birds fed on prey remain left by the feeding otters, on small fish captured by otters when these were satiated and playing, or on prey displaced by otters. Our observations are consistent with facilitation and commensalism: piscivorous birds gained feeding opportunities provided by the otters, with no apparent costs or benefits to the latter. Similar feeding associations have been described between other species of otters and piscivorous birds (kingfishers, herons, egrets, storks) in Asia, South America and Southern Africa, but had not yet been described in Europe. The occurrence of piscivorous bird–otter associations in different species and regions suggests that this commensalism may be often overlooked but widespread. We have shown that the association can be frequent and is context‐dependent, with benefits for associating birds depending on otters´ behaviour and targeted prey.     

The Influence of Social Environment: Behavior of Unrelated Adults Affects Future Juvenile Behaviors

Juveniles' behaviors are often influenced by the behaviors of conspecifics. Most experimental studies of the influence of conspecific behavior vary the social environment by the presence or absence of conspecifics or investigate the impact of the outcome of social encounters (winner/loser effects) but less frequently expose individuals to variation in behavioral phenotypes present in the social environment. Based on previous work showing that juveniles of the salamander Plethodon cinereus are likely to interact frequently with non‐parental adults, I hypothesized that territorial adults in the social environment alter the future behaviors of juveniles. I measured the intracohort social behaviors of juvenile salamanders collected from two geographic areas, Michigan (MI) and Virginia (VA), before and after housing with ostensibly territorial (VA) or non‐territorial (MI) adults. There were overall effects of adult territoriality and aggression on the behavior of juveniles. However, juveniles from populations in MI were especially susceptible to behavioral modification. Compared with behaviors prior to being housed with adults, MI juveniles increased investigatory and escape behaviors in juvenile–juvenile interactions after being housed with adults that displayed territorial behaviors and decreased investigatory and escape behaviors after being housed with non‐territorial adults. This study shows that not only is a specific behavior, territoriality of adult salamanders, a social environment that modifies future juvenile behaviors, but the effects of social environment may differ between populations.     

Social buffering in adult male rhesus macaques (Macaca mulatta): Effects of stressful events in single vs. pair housing

Background The purpose of this study was to test whether long‐term pair housing of male rhesus macaques ameliorated negative responses to stressful events that can occur in the course of routine husbandry or research procedures. Methods Twelve singly housed individuals were videotaped during two potentially stressful events before and after social introduction into pairs. During each stressor, abnormal behavior and anxiety‐related behavior were quantified from videotape. Results When visually exposed to the restraint and anesthesia of other monkeys, subjects showed significantly reduced frequencies of abnormal behavior when pair‐housed in comparison to their reactions when housed singly. Noisy and disruptive conversation between technicians standing immediately in front of the subjects’ cage did not elicit the same reduction in abnormal behavior. Neither test showed a significant difference across housing settings for anxiety‐related behaviors. Conclusions These findings suggest that pair housing buffers adult male rhesus macaques against common stressors in the laboratory setting.     

Characterizing habitat preference of Eurasian river otter (Lutra lutra) in streams using a self-organizing map

We studied the habitat preferences of Eurasian river otters (Lutra lutra) using the distribution patterns of the numbers of spraints and sprainting spots of otters, as well as related environmental variables (habitat zone, river management, bank type, vegetation coverage, width, depth, etc.) in two streams. The numbers of otter spraints and sprainting spots were sampled monthly in two streams on Geoje Island, Republic of Korea, from January to December 2004. Additional environmental variables were measured at the sampling sites. A self-organizing map (SOM), which is an unsupervised artificial neural network, was used to characterize the habitat preferences of otters. In our results, the SOM classified three different groups of study sites based on their habitat conditions, and the habitat differences were effectively visualized on the trained SOM map. Otters showed spatial and temporal dynamics in the numbers of spraints and sprainting spots, and revealed habitat preferences for shallow, narrow areas of streams and edges of water that were not far from reservoirs but covered with trees and shrubs. Additionally, otters preferred an environment in which weirs reduced the drift of water and gathered fishes and had a natural type of stream bank; these findings are relevant for river management. Otters adapted to places close to roads, residential areas, and agricultural areas with some tolerance of human interference.