A basic overview of the study: Every day I watch the animals in the study group and write down what they are doing every minute for 30 minutes. After this, I place an item of enrichment in their enclosure and watch them again for another 30 minutes to see if their level of interest is raised and if they enjoy what I have given them. I am able to watch and “enrich” six off-exhibit enclosures per day. The enrichment items that I have used thus far includes many different scents (pine, cinnamon, sage), tall plastic cylinders with scents inside, large rubber jolly balls, thick plastic Boomer balls, car wash brushes, and mirrors.
The animals that I am working with are deer species (Indochinese and Mandarin sika, Malayan sambar, Barbary red deer, white lipped deer, pudu, and tufted deer), antelope species (nyala, addra, and roan), and equid species (Przewalski’s horse and Somali wild ass). The horses have been the most fun to work with because they seem to react to everything. For example: if I put in a scent, they sniff every location; if I put in an empty keg, they play with it, kicking and licking; if I put in a jolly ball, they nudge it with their noses.
The tufted deer and the pudu are wonderful as well because they are just so cute—it is hard not to love them, no matter how they react to the enrichment. The most difficult animal has proven to be the sika deer. I seem to be their most entertaining form of enrichment. They like to alert the other animals of my presence by sounding warning calls, stomping their feet, and walking around in circles. The scents do not particularly interest them, they do not like to see themselves in the mirror, and the cylinder with scent only entertained their noses for a few minutes. I, however, am determined to find something that suits them!
My personal favorite item of enrichment has been the mirror. The Przewalski’s horses have loved staring at themselves and even seem to fight over which one gets to stand in front of it the longest. The tufted deer was uncertain of it at first and waited about five minutes before even going near the mirror. However, after he was comfortable, he sat in front of the mirror for almost five minutes, moving his head from side to side, pawing at the mirror’s base, licking, and even nibbling! The best part is that every few minutes, after walking around a little, he would come back for more.
I am hoping that by the end of this study the mammal keepers that work with these animals will have an easier time knowing what items of enrichment to put in the enclosures that would benefit the animals the most. I have the time to observe these animals and find out what makes them happy.
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Cassidy Horn is a student at Stanford University and a summer intern at the San Diego Zoo’s Wild Animal Park. For more information about enrichment, see posts New View of Enrichment and Somali Wild Ass Enrichment.


Welcome Cassidy, It’s so much fun to watch there reaction to different sounds, sights and smells. I will be interested to hear how things are progressing. Enjoy your summer and your animal students
Fascinating and creative!!
Do the sika deer respond to food or treats as enrichments?
Love the mirror description. Wish we could see some of your work on video!
Good luck for the remainder of your study this summer.
I wondered how they knew what the animals like. Have fun figuring out the sika deer. Would love to hear the results.
#2 Mae
I am trying to stay away from introducing treats and food into the enrichment, because I know that they will most likely respond positively to that; they will find a way to get the food and then that will be it! I figure that if I can find something they like that does not involve food or treats, it will be more entertaining for them in the long run (not just fun until the food or treat is gone). It has been difficult to work without items such as treats with the deer, but I know they like foraging. I’m still trying to avoid food; however, if it comes to the point where it’s my last option, I’m working on designing something that they have to “sift” through to get the treats; even in the wild, deer do not get fed their treats/food in a nice bowl like they do here. Thus, I figure if they have to work for their food, or at least spend some time finding it and getting to it, it will be better than nothing.
Thanks for posting, Cassidy. Your adventures are very interesting. Consider yourself fortunate to be working at one of the world’s best zoos.