A couple of weeks back I published a post about how Jaegers and other predatory birds are frequently found around herds of caribou. Bird/Mammal and other interspecific relationships are hardly novel. Researchers have documented these interactions across the planet. Still, I really dig the concept, the details and always enjoy learning about more. So I was pleased when I stumbled on another cool one.
Last week I was camped near Macharak Lake, in the Noatak Valley. It was the final day of a week-long canoe trip. I’d just finished up a very long day of paddling, and lugging gear from the river to the lake shore. We’d set up camp atop an old moraine that makes up the northwestern side of the lake. Looking to the south, Macharak spread blue and bright, the surface tossed by wind-driven chop. The mountains all around were lit by the late evening sun. It was, well… awesome. Embarrassingly, I was so exhausted, I left the view behind, crawled into my tent and gratefully climbed into my sleeping bag.
I lay and read for a few minutes, my eyelids quickly growing heavy, and as I was about to close my book, a high, long, howl came whining across the lake. I allowed my eyes to close, but I was no longer tired. Instead, I lay and listened to the music of a single wolf.
The animal sang for just a few minutes, it’s voice a mix of howls and occasional sharp, high-pitched barks. There was no response from another wolf, this may have been the only one for miles, but still it howled.
What, you ask, does this have to do with birds? Well, while researching for another post here, I found an article from a 1978 issue of the ornithological journal The Condor. The title caught my attention: “Ravens Attracted to Wolf Howling”.
Ravens make a good portion of their living from carrion left behind after wolf kills. Often these kills are found through random searching, but they also use the calls of other ravens, and according to the author of this paper, the howls of wolves. Wolves howl for a lot of reasons (more on that in a future post), but often howl around recent kills. This tendency draws the attention of ravens looking for scraps.
Fred H. Harrington, the author of the paper, did a little howling himself to prove his theory. In the incidents he reports, when he gave out a howl, passing ravens would immediately change direction to come investigate. He found that ravens were most responsive during late fall and winter, which is also the season when wolves most frequently hunt in large, vocally-communicating packs.
Cool. But it’s not surprising considering how intelligent Ravens are. They solve problems on a lot of levels, and following wolves seems like a clear shortcut to winter food. Makes me want to try out Harrington’s experiment for myself. This winter, I’ll have to see if I can howl in a few ravens.
Had never considered the verbal component of raven attraction to a kill site! Wow, great to think about. Classically I think about finding kill sites as a visual enterprise. I was just discussing raven consumption of wolf kills with a FWS employee in the Yukon Flats NWR last week. Our discussion piqued my interested to look at consumption rates at kills. Incredible how much they can take, and quickly! Small packs (like those found in the low density moose population of Yukon Flats) cannot defend against the ravens as well as a large pack. Hence, kill rates are kept high partially by scavenging. Petra Kaczensky et al. report “Ravens were by far the main scavengers and on average, we counted 18.5 ± 12.7 (SD) ravens and documented removal of 14.1 ± 1.3 (SE) kg biomass each day (N = 53 observation days)”
Kaczensky, Petra, Robert D. Hayes, and Christoph Promberger. “Effect of raven Corvus corax scavenging on the kill rates of wolf Canis lupus packs.” Wildlife Biology 11.2 (2005): 101-108.
Whoa. That’s crazy! I never would have considered raven scavenging as a competitive factor for wolves. I’ve watched wolves chase ravens off kills, but I always figured they were just an annoyance. Very cool information and thanks for the link. I’ll take a look at the paper.