Prey preference of the North American River Otter (Lontra canadensis), evaluated based on optimal foraging theory: A thesis by Leslie Thompson

Prey preference of the North American river otter (Lontra canadensis) was studied in a
captive population and evaluated according to optimal foraging theory. Optimal foraging theory can provide explanations and help make predictions about prey preferences based on the theory that animals should maximize their caloric intake and minimize energy output while foraging.

Seneca Park Zoo Otter Photo by Jeff Gerew

To determine how otter prey preferences match up with this optimal foraging models an RIT graduate student, Leslie Thompson, released Live sunfish, brown trout, and crayfish into the otter exhibit pool.  The otter’s search, chase, and handling/eating times were recorded.

When provided with choice of sizes (size trials), otters showed a significant preference for catching and eating large prey first. When given a choice of species (species trials), otters significantly preferred to catch and eat brown trout first. Also, when given dead food items on land the brown trout remained the favorite.

Brown Trout

The preference for brown trout was expected as the prey provided significantly more energy per unit time spent catching it. Though the brown trout did not have significantly more calories than the sunfish, they did require significantly less energy to catch and consume.  Therefore,  preferences for brown trout matched Thompson’s predictions for all the size trials and for all species trials.

Captive river otters exhibit prey preferences that match with predictions based on optimal foraging theory, which can provide insight into dietary habits of wild otter populations. Once again, research with valuable implications for wild animals comes from researchers and Zoo staff working together.

Environmental Enrichment Effects on the Activity of a Nearctic River Otter: A Thesis by Kenny Nelson

Admiral the North American River Otter (Photo by Jeff Gerew)

A masters thesis completed by Kenny Nelson at RIT was designed to determine how environmental enrichment affected the behavior of a Seneca Park Zoo North American River Otter.  Enrichment is regularly used in Zoos to change a behavior in a captive environment.  This can improve animal welfare by bringing out natural behaviors and combating stereotypic behaviors. A stereotypic behavior is the loss of naturalistic behaviors in captive animals, which are replaced by abnormal behaviors such as pacing.  For the otter in the study, the ZooKeeping staff was seeing a repetitive swimming behavior.

Enrichment can be adding objects, smells, or food to an animal’s exhibit or even modifying enclosure design in an attempt to increase naturalist behaviors in a captive environment.  For his work, Nelson presented four enrichment initiatives to the otter.  These items included live fish, frozen fish, a swim tube, and PVC pipe scent tubes.  These items were giving in a random order and placed throughout the exhibit.

Admiral the North American River Otter Photo by Jeff Gerew

The results showed that food (i.e. live fish and to a lesser degree frozen fish) was most effective in deterring a stereotyped swimming pattern.  Nelson also observed a pattern of where and when the otter spent most of his time; data showed that the otter preferred to spend mornings in the lower level of the exhibit and the afternoons in the upper level.  Food enrichment was more effective when given in the afternoon suggesting that the otters stereotypic behavior was occurring out of a lack of ability to forage.

Results like these can be an enormous help to animal husbandry staff at Zoos and Aquariums all around the country.  Looking at these results the animal husbandry staff can create more opportunities for the animal to forage (by adding enrichment) and therefore increase the animal’s welfare (by decreasing stereotypic behaviors). Studies like this can determine which kind of enrichment works best for a specific species.  Projects like these are exciting ways for researchers and Zoo staff to work together to better the lives of animals.

Check out this wonderful video taken at the San Diego Zoo.  You may remember one of our first posts about Why we love otters, where we discuss Zoo visitor’s fascination with these amazing animals, and some reasons why we are all so fascinated.  This video is one of the best examples of that I have ever seen.( Video of boy racing an otter at the San Diego Zoo). Do you think this little boy and his family will ever forget this encounter?  And now that this video has been shared across the globe, we can all share in that memory and we can all understand a little better just why we love otters!

Otter Crossing Sign in the UK

While searching for some fun new otter photos, which you will find under the Otter Photos section of the blog, I came across the above photo.  This is an otter crossing sign found in the United Kingdom (UK).  The UK is home to the Eurasian river otter (Lutra lutra) , which is a one of the 13 otter species and is listed at Near Threatened with ICUN Red List.  According to ICUN one of the many reasons for the decline of the Eurasian river otter is car strikes.  This is a good thing to remember if you live in river otter habitat.  As successful reintroduction projects bring otters back to areas populated by humans we must remember to brake for otters!

Last week I was fortunate enough to go to a workshop with fellow otter educators and researchers from all around the world at the Columbus Zoo.   This was a strategic planning meeting to develop education goals and strategies for the Association of Zoos and Aquariums (AZA)‘s Otter Species Survival Program (SSP).  

Soon I will post a summary of this workshop and feature research stories about some of the researchers who attended the workshop.  For now, here is a blog I posted on the Seneca Park Zoo’s Educator’s Blog about the event, Working Together to Help Otters.
More to come soon!