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<em>By Heather Neldner, Zookeeper
Milwaukee County Zoological Gardens, Milwaukee, WI</em>

In September of 2005, we started an enrichment program for the flock of Humboldt penguins (<em>Spheniscus humboldti</em>) at the Milwaukee County Zoo with the goals of encouraging the birds to swim and to interact with each other more. Two of the birds (Houdini &amp; Arisco) have chronic foot issues and we were hoping they would improve with more swimming.

The Milwaukee County Zoo’s Humboldt Penguin exhibit is the first exhibit guests see when entering the zoo. It is an open air exhibit, with a large rocky structure and a 15,000-gallon pool. The birds have access to the exhibit and indoor holding area 24/7 all year long. We currently house 6.5 penguins with the oldest bird being 23 years old and the youngest having hatched in May of 2008.  Prior to starting a formal enrichment program for the birds, they were only offered a Boomer Ball®, some plastic bottles with colored objects sealed inside them, and ice blocks once in a while to play with. Most of their enrichment was in the form of interacting with the public through the glass viewing windows.

The first step in the enrichment program process was to complete the paperwork to obtain approval, via a three-level process, for the items we chose.  The first level is obtaining supervisor approval, then it moves on to our curator for second approval, and then on to the veterinarian for final approval. Currently we have 30 items approved for our birds but not all of the items have been utilized as yet. Most of the items are dog toys because they are very durable and most of them float.

Toys are only given in the pool while we can supervise the birds to make sure they interact with them appropriately.  This also gives us the opportunity to do enrichment talks during this time, if the public seems interested in what is going on. We are also hoping (and it has seemed effective) that if toys are not in the pool all the time, people will be less likely to toss items in the pool. If a bird is held inside away from the others for any reason (sickness, medical work-ups, weaning, etc) they can have a durable toy, such as a Boomer Ball®, plastic keys or a confetti bottle all the time to play with to prevent boredom. Our Graphics Department has made us a fantastic sign that explains enrichment to the public and explains why toys are only given when supervised.
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<strong>Mariano playing with a fabric Frisbee® (Photo: H. Neldner)</strong>

It is very rare that we have any aggression between the birds (exhibited as displacement, or chasing) when playing with the toys. They all appear to “share” the toys pretty well. Most of the birds have shown a high level of interest in the toys and rarely do any birds show fear or avoidance of a new item. If the birds appear to be avoiding a toy, I will play with the toy myself to demonstrate it is “ok” and will encourage them to join me. Usually this does the trick and the more curious penguins will start playing with the toy, with the others occasionally joining later.

Toys are rotated often since the penguins do seem to get bored with individual toys if they are offered too frequently and will stop interacting with those items.  We have made an enrichment calendar to help coordinate this.  Alternatively, the birds never seem to get tired of some toys.  These include a small white Boomer Ball®, bubbles, confetti bottles and a tennis ball turtle. Their play sessions don’t always last a long time, with a notable decrease in interactions with the toys after about 15 minutes or so frequently observed. If we sit outside and encourage the play, with praise and by interacting with the birds and the toy - for example, tossing the Frisbee® out for Houdini to “fetch” -  this will encourage the birds to stay in the water longer and play with the items more. If there is a large crowd of people out by the exhibit cheering the birds on, they will play with the toys longer and more vigorously. They appear to enjoy the attention!

Some of their favorite toys include:  tennis ball turtle, tennis ball dumbbell, fabric Frisbee®, confetti bottle (Neldner, 2008), small Boomer Ball®, and floating plastic dumbbell. Houdini frequently puts the floating dumbbell on his back and……………

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