Thursday, September 30, 2010

Why Black Bears Eat Insects

Shenandoah National Park Black Bears

Why would a large animal such as a Black Bear want to consume small insects? Because the larva of insects such as ants, termites, beetles, yellow jackets, bees, wasps contain 80% to 90% protein. To put this into perspective, beef is about 20% protein, so 4 or 5 grubs will give a bear the same protein as a full size burger (grub is basically the larva of beetles, bees and wasps). When you see bears flipping rocks or digging into logs, this is generally the reason for them doing so.

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Black Bears dig up ant colonies in spite of the ants' defensive formic acid onslaught to consume their pupae and larvae (collectively known as brood). They dig up hornets' nests to retrieve the brood comb that contains the larvae, and they suffer the persistent stings. A bears skin is tough and their fur is very thick so the only places that a black bear can be stung so that it really feels it is on the lips, near the eyelids, and on the tip of the ears.

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In Summer, ant pupae and larvae become abundant. Ant brood is a major food from late spring until mid to late summer. Ants undergo complete metamorphosis, much like that of butterflies, where they pass from egg to larva to pupa before maturing into an adult ant. Bears consider this as a top favorite food source and is a huge part of their diet at this time of year. It is a delicacy for cubs eating their first solid foods.

Bears find brood by keying in on pheromones and other chemicals that ants use for communication and defense (watch the video clip below to see this behavior). Bears attempt to eat brood cleanly without getting a lot of soil, debris, and adult ants. They do this most easily with colonies under rocks, moss, and ground litter. They flip over the rocks or other cover and get the brood with a few flicks of their sticky tongues.

Click on a thumbnail below for larger view

About the above photos: there are some huge ant mounds (colonies) that exist across from the Old Rag View overlook at Shenandoah National Park (in the Central District). One morning in early Summer 2009 as I was driving by that overlook, I noticed they had all been ripped up and I was positive that a bear had done it. Well after several weeks, the ants eventually rebuilt their colonies. But one August evening as I was driving by the mounds, I was fortunate enough to witness firsthand a bear invading them -- and what a show it was!

A short video clip of a Black Bear raiding ant colonies

View the clip on YouTube

For more black bear photos, information and video clips, visit the black bears section of my Web site.