What the cluck?!

6 03 2016

Behold the ruffled feathers of a hen who’s been placed in a dark box, then exposed to a camera flash. Poor girl, this did make her (and each of her similarly-treated flockmates) jump.

startle 1

But this jump was just what we were hoping for. What she was showing, and what Misha could pick up via the forceplate she was standing on, was a perfect startle reflex. Beginning with a neck retraction (and probably an eye blink, though the videos are too blurred to detect this), within about 300ms she jumps – as beautifully illustrated below, followed by a few ‘aftershocks’.

hen startle

Startle reflexes are potentially valuable in welfare assessment because in humans and rats, they increase when subjects are in states of anxiety or fear. MSc student Elyse Germain had tried to develop a method for hens before, but despite exposing hens to a loud horn found no clear signs of startle. I think her stimulus had too slow and ‘soggy’ an onset time (compared to the near instantaneous ‘step function’ of a flash), and the birds were also too mobile – possibly creating ‘pre pulse’-like inhibiting effects on startle, and definitely making it really hard to see anything. With the flash in the dark box, we knew we were solving the first problem, but through sheer serendipity we also solved the second as well because it made the hens so lovely and still before the startle stimulus.

Next step: can Misha now modify startle by making the hens’ states more positive (for example, by conditioning them to associate the box with treats)? This would really show it’s homologous to what is seen in mammals.