Study on How to Better Design Healthier and More Effective Exhibits for Otters

Abstract

It is important to study how animals utilize their enclosures to know how to better design healthier and more effective exhibits. This study attempted to determine if the otters in the Lost Forest mixed-species exhibit at the San Diego Zoo used any one area of their enclosure more than others. It was reported that two otters were kept in the exhibit, but during the study only one was observed. It also appeared that the otter was prevented from using areas 1, 2, and 3. The otter was also prevented at times from moving between Areas 4 and 5. This study was not able to make a conclusion about the otters’ preference for habitat use. The need to study and understand how otters use their enclosures is still an important issue in the long term care of otters in captivity.

Introduction

The spotted-necked otter (SNO) (Hydrictis maculicollis) is a member of the mustelidae family and is found throughout central and some portions of south east Africa. They are somewhat more aquatic than many other species of river otter but are still land animals that use water for feeding, movement, and play.

The International Union for Conservation of Nature and Natural Resources (IUCN) Red List of Threatened Species lists the SNO as Near Threatened. The primary threats to SNO come from a rapidly increasing human population (Rowe-Rowe 2000). Urban expansion results in a loss of habitat as well as industrial pollution. There is an increasing demand to produce food and grow cash crops. More natural habitat is destroyed each year. Overgrazing is also a serious concern, resulting in increased water runoff, loss of soil, and siltation of streams. The impact of global climate change throughout Africa (Hendrix and Glaser 2007) also has the potential of decreasing suitable habitat for otters and increasing human/otter conflict for increasingly scarce resources such as water, land, and fish. Both this decrease in suitable habitat and increase in human/otter conflict are currently occurring and will certainly increase over the next three generations.

In the wild otters spend more of their time resting than being active (58% to 42%, respectively) (Perrin 2000), so facilities need to provide for comfortable and secure locations for resting with minimal disturbances, either from guests or other species.

Otters have been kept in captivity for many decades now, though for not nearly as long of a time as many other types of animals. Much research has been done on the health and breeding of captive otters, as well as non-structural environmental enrichments such as toys and food placement, but little on their actual utilization of the exhibits. Knowing how an otter spends its time may provide insight into how future enclosures should be designed.

Enclosures should have a land to water ratio of 5:1. Surfaces should be as natural as possible and include wood chips, soil, sand, and rock. Surfaces such as concrete should be used as little as possible. The otters need to have significant places where they can rest and dry out, with the option for shade or sun, as well as protection from rain. There also needs to be variety in water feature design, with different shapes and depths and faster or slower moving water to provide diversity. Because SNO enjoy waterfalls, islands, and mud slides, as many of these features should be included as is feasible. The complexity of the enclosure and an appropriate land/water ratio is important for maintaining a safe psychological and physical environment for the otters.

It also is imperative to provide areas that the otters can thoroughly dry their coats. Supplying multiple dry, loose substrates such as mulch, sand and soil allows for proper grooming and healthy fur. Care should be taken to change substrates often so they do not become overly soiled and remain an attractive choice for grooming.

Spotted‐necked otters do well in some mixed‐species exhibits providing care has been taken to address the unique challenges these groupings provide. When attempting mixed‐species exhibits care should be taken to ensure all animals are compatible and have access to all exhibit features required to meet their needs; this includes food, enrichment items, and water.

Otters enjoy digging, climbing, rubbing their bodies on substrates or furnishings, exploring exhibit features, swimming, playing and interacting with other species (care must be taken these interactions do not become aggressive). An exhibit that provides these stimulations will best ensure healthy otters.

Fifty years ago recommendations were made that outlined the need for large, complex land areas and other features key to ensuring high levels of otter welfare, which many ex situ facilities, such as zoos, aquariums, and rehabilitation facilities, have now adopted. Increased welfare of captive otters is due partially from improved environmental conditions such as better habitat design, and partially from improved understanding of otter nutritional and health needs.

The ability to role/rub on various surfaces is behaviorally important to the maintenance of a healthy coat. Otters also like to dig and root around, and the health of their feet can be compromised by continually damp or wet surfaces

Appropriate exhibit size. Too often otters are viewed as small animals and thus kept in small spaces

Zoos and aquariums have improved the health care of otters consistently over the years. Partially this is due to improved environmental conditions

A new direction in habitat design is currently being promoted, which suggests a move toward allowing animals greater choice and control over their environment through concepts such as "rotation exhibits" "raceway networks". If these concepts are applied to otters in the future, particularly allowing them to move between exhibits of compatible species, overall welfare may improve via extension of their ability to choose where they an increase in their daily ranging abilities, an increase in their living-space complexity, the provision of opportunities for group members to join stimulating bored otters through enhanced foraging

Creating factual, documented activity budgets for individual otters is a first step. A good second step would be to assess enclosure usage patterns for each animal by mapping where, and how long, each otter is spending its time.

Methods

The Lost Forest exhibit is a roughly Y-shaped enclosure with the arms opening to the north and west, a walkway passing over the junction in the middle, and a rounded area to the southwest that houses the monkeys. This is easily divided into five areas of the enclosure where the otters’ location will be charted. Area 1: Starting at the end of the left arm, as seen from the junction of the Y, there is an elevated section with a deep pool and viewing glass accessible to the otters by climbing a waterfall structure. Area 2: In the middle of the Y is a pool with several rocks. Area 3: Around to the right arm is a long rocky canyon with flowing water. Area 4: There is a tunnel and presumably den underneath the walkway that is not visible. Area 5: At the base of the Y is a wide area the otters share with monkeys.

Observations were conducted over six 2-hour blocks during the week of July 15, 2018 using a focal follow. Four observations were conducted in the evening, one in the afternoon, and one in the morning. A multi-timer was used to record the amount of time in seconds the otter spent in each area. Area 4 included times when the otter was not visible and assumed to be in the underground den. Because there was no one vantage point to see the entire enclosure I moved around as needed to keep track of the otter.

Results

The only otter visible during the observation period was Mzee, a 22-year-old male. Mzee did not enter Areas 1, 2 or 3 during the observation periods. He spent 61% of his time in Area 4, the tunnel, and 39% of his time in Area 5 with the monkeys.

There were no statistically significant differences between the group means for the five areas as determined by one-way ANOVA (F(1,8) = 1.787, p = 0.22).

Discussion

During the observation periods the otter Mzee was not given free use of its habitat. The area on the northwest side of the walkway appeared to be not in use at all, with more debris and leaf litter floating on the surface than at previous visits. A drain was clogged with grass and leaves and was not serviced during the week of observations. I was not able to see if that side of the enclosure was physically closed off, but that seemed to be the case. During several of the observations I was able to see that the opening between Areas 4 and 5 was closed, either shutting the otter in Area 4 or outside of Area 4. During one observation period the otter was asleep on the grass in Area 5 the entire time.

Conclusion

It is important for future exhibit designs to know how a specific group or species of otters likes to spend their time and how they utilize their enclosures.