Enrichment Effectiveness in a Captive Pinniped Population


Chelsea Corson

Lisa V. Michel

Dayna Zaks


Spring 2004


Animal Behavior


Instructor: Becky Burton


In this experiment, a hybrid meta-analysis was performed to determine enrichment effectiveness in a captive population of pinnipeds including California sea lions (Zalophus californianus) and an Atlantic harbor seal (Phoca vitulina).It was hypothesized that the food enrichment would elicit more activity and therefore be more effective than sensory or novel object enrichment.From the data collected, it was found that the hypothesis was supported by an ANOVA p-value of 0.0231.

Keywords:Enrichment, captive, California sea lion, Atlantic harbor seal, pinniped



Environmental enrichment is primarily utilized for optimal psychological and physiological well being for captive animals.Enrichment has been developed so that handlers and trainers are able to enhance the quality of the animalís lives (Shepherdson 1998).Environmental enrichment is defined as any stimulus that is added to the animalís environment that becomes both mentally and physically stimulating.

††††††††††† Enrichment can come in different forms, from a large rubber ball to different food items the animal may enjoy.The animal caretakers will often use training as a form of enrichment.Animals are trained to present different parts of their bodies including their teeth.This helps when the animal may need to be examined by a veterinarian, providing medical care in a stress free environment.The animals have been desensitized to being around humans and being given medical treatment (Cox et al. 1996).Through desensitization, the animals become more comfortable with some of the enrichment or stimuli that may actually start off as being fear provoking (Desmond and Laule 1998).

††††††††††† Typically when an animal has been desensitized to being around humans and being in captivity, it is more likely to thrive.†† As well, the animals are more likely to return to their natural breeding patterns due to the reduction of stress.Captive animal programs are attempting to provide habitat that will bring out the natural instincts of each animal (Caristead and Shepherdson 1994).Not only do the animals become desensitized, but they also become habituated to their environments.Habituation is considered learned and it changes the behavior of the animal, reducing stress (Kuczaj et al. 1998).

Another type of enrichment is play.This may be one of the most important types of enrichment since it is an essential part of development (Kuczaj et al. 1998).Animals are provided with toys to manipulate and explore.Animals that are social are placed with other animals of the same species to practice their natural behaviors including games of chase and wrestling (Kuczaj et al. 1998).

Devices for play may be as simple as a wooden block.For the blue fox (Alopex lagopus) a wooden block was used for play enrichment so that the fox may gnaw at it to reduce plaque and gingivitis (Korhonen 2000).However, if an animal has an object on a regular basis, they may tire of it and discontinue using it, as with some small primates that continuously interacted with the same object and then became disinterested in it (Ben-Ari 2001).This has signified that all enrichment should be done in moderation.

For this experiment, we did a hybrid meta-analysis of environmental enrichment data from Oceans of Fun, seal and sea lion show, located at the Milwaukee County Zoo.Harbor seals (Phoca vitulina) and California seal lions (Zalphus californianus) are pinnipeds, or fin-footed marine mammals (Marine Mammal Center 2002).Between the two of them the California sea lion is a more social animal than the seal.They also have different physical characteristics; sea lions have an external ear flap while seals do not.Also, a sea lionís back flippers are more useful for them on land; they can rotate their hind flippers and use them like feet.Sea lions also tend to be larger then seals.

Table 1.Average weight of both California sea lions and harbor seals (Marine Mammal Center 2002)

Average Weight



Sea Lions

390 kg

110 kg


140-150 kg

130-140 kg



The seals and sea lions in this study have had long-term environmental enrichment and training.The different types of enrichment used for these animals were novel object enrichment (example: ball or Frisbee), food enrichment (example: fish frozen in blocks of ice) and sensory enrichment (example: audio whale songs).We hypothesized that food enrichment would be the most effective since food is a primary reinforcement; they need it to survive.



††††††††††† A captive population of six California sea lions and one Atlantic harbor seal was utilized for this experiment.These animals are residence at Oceans of Fun, the seal and sea lion show located within the Milwaukee County Zoo, in Milwaukee, Wisconsin.At Oceans of Fun, an existing enrichment program developed by Tami Draeger and Bonnie Gahan, trainers at Oceans of Fun, has been in place for approximately three years and was used for this experiment.Each of the enrichment devices is categorized into three groups including novel object (example: Frisbee or ball), sensory (example: running water) and food enrichment (example: fish frozen in blocks of ice).The scale to rate the effectiveness of the enrichment device for each animal was provided by Oceans of Fun (Table 2).

Table 2: Enrichment scores and descriptions, provided by Oceans of Fun

Enrichment Score

Score Description




Inspected then Ignored


Continued Curiosity


Very Enriching


To rate the effectiveness of the enrichment device for each animal, the behavior of the animalís activity concerning the enrichment device was observed.Scores 1 and 2 are self-explanatory, however a score of 3 and 4 are not.The difference between a 3 and 4 is the interaction with the device and the animalís activity level.For example, if the enrichment device is a ball and the animal continuously inspects the ball from a short distance the animal would receive a score of 3.However, if the animal pushed the ball around the pool during the session, they would then receive a score of 4 due to the high interaction with the object.

For each of the enrichment trials, the enrichment device was placed either in or near the main pool (depending on the object) and the behavior of the animals involved was observed for approximately 15 to 20 minutes.Following the observation time, the behaviors elicited by the animals was recorded and each animal was given an enrichment score based on their behavior.Since this experiment was a hybrid-meta analysis, data were collected at Oceans of Fun between January of 2003 to March of 2004 by both Oceans of Fun employees and the experimenters.In total, 432 scores were recorded and utilized for analysis, 43 being observed and recorded by the experimenters.

Once all of the scores were collected, they were compiled into groups based on device type and in order to analyze the data, an analysis of variance (ANOVA) using InStat was performed.For each of the enrichment categories averages were determined.A graph of these averages was created using Excel and error bars were put in place using the standard error calculated from the raw data (See figure).



††††††††††† From the ANOVA analysis, it was found that there was an overall significant difference between the enrichment types (p-value of 0.0231).An analysis revealed that there were significant differences between novel object and food enrichment as well as sensory and food enrichment (See Figure 1).However, there was no significant difference in the effectiveness of novel object and sensory enrichment.

Figure 1: Average enrichment scores of a captive pinniped population verses the enrichment type



††††††††††† The results confirm the hypothesis that activity is dependent on type of enrichment and that the type of enrichment will yield different levels of interest.Food was more effective in eliciting activity than novel object and sensory.Using a hybrid meta-analysis we were able to compile a significant amount of raw data that may have helped to further support our hypothesis.Food, being a primary resource, is difficult to measure up against sensory and novel object enrichment since it will usually overcome the others in the area of interest; however, food is also dependent on seasonal variation.In the summer months sea lions often lessen their food intake due to high interest in mating, therefore food enrichment may be less effective in the summer months.Males consume 13.5-18 kg daily while females consume approximately 6.75-11.25 kg.Their diet intake varies with the seasons and consists of capelin and herring.

††††††††††† Variability within the categories of enrichment may have been an additional factor. Some objects may have a different effect than others on the sea lions.For example, the novel objects had the most variability in type of enrichment and so the sea lions may have responded differently to them individually.

††††††††††† In addition to the variability within the enrichment categories, age is also an important factor in measuring activity.As discussed in the introduction, pups exhibit a higher level of playful behavior than do their elders and therefore will respond to enrichment in a higher number of cases and at different levels than the older sea lions.We chose not to use age in this experiment due to other variables, but we do recognize that it may have had an impact in this study.

††††††††††† An interesting question arises with this study of why the animals did not respond to sensory more than novel objects.It seems intuitive that an animal would respond to something stimulating and so this creates a new type of study that might investigate the physiological reasons for why novel objects might get more response.One theory may be that novel objects are more common than sensory type objects and so they choose to interact with it more. Also, it would be interesting to see which enrichment of the two would be selected if both were presented to them.


Literature Cited

Ben-Ari, Elia. 2001. Environmental enrichment for small primates. Bioscience. Vol. 51, Issue 3. Retrieved March 7, 2004 from EBSCO database.


Caristead, Kathy, Shepherdson, David. 1994. Effects of environmental enrichment on reproduction. Zoo Biology. Vol. 13, no. 5, 447-458.


Cox, Marie, Gaglione, Eric, Pamela, Prowten, Noonan, Michael. 1996. Food Preferences Communicated via Symbol Discrimination by California Sea Lion (Zalophus californianus). Aquarium of Niagara and Canisius College. Aquatic Mammals. Vol. 22, 3-10.


Korhonen, H.T. 2000. Enrichment value of wooden blocks for famed blue foxes. Animal Welfare. Vol. 9, 177-191. Retrieved March 7, 2004 from EBSCO database.


Kuczaj, S., Lacinak, C., Turner, T. 1998. Environmental enrichment for marine mammals at Sea World. In D. Shepherdson, J. Mellen and M. Hutchins, Second Nature: Environmental Enrichment for Captive Animals (p 314-328). Washington: Smithsonian Institution Press.


Laule, Gail, Desmond, Tim. 1998. Positive reinforcement training as an enrichment strategy. In D. Shepherdson, J. Mellen and M. Hutchins, Second Nature: Environmental Enrichment for Captive Animals (p 302-313). Washington: Smithsonian Institution Press.


Marine Mammal Center. 2002. The Pinnipeds. Retrieved March 7, 2004 from www.tmmc.org/index.asp.


Shepherdson, David. 1998.Tracing the path of environmental enrichment in zoos. In D. Shepherdson, J. Mellen and M. Hutchins, Second Nature: Environmental Enrichment for Captive Animals (p 1-10). Washington: Smithsonian Institution Press.