A symbiotic relationship is one that benefits members of two different species or groups.
Last summer I wrote about the symbiotic relationship between ravens and wolves. While I wish I could personally observe that relationship in action, wolves are too elusive (as they should be) so it’s only the ravens I’m privileged to see up close.
A month later I wrote about how my dog Finn takes umbrage when two resident ravens fly over the yard and house. Being an Australian shepherd, he does his best to herd them away, barking and running across the yard, stopped only by the fence. In his mind, he always succeeds because the ravens depart, continuing on their way, landing in tall trees some distance away.
Recently I’ve observed the two resident ravens coming closer, landing in my field a few yards beyond the dogs’ fence, walking around on the snow and occasionally pecking at something.
This was new.
On December 20th, while the dogs and I were inside the house, I watched both ravens standing in the snowy field. The snow wasn’t very deep, so I was finally able to put two-and-two together: these ravens had discovered the bone yard.
Let me explain. As a treat, about once a week I give the boys marrow bones. They’re marrow-rich beef femur bones cut by the store butcher into sections of one to three inches. It takes the boys 20-30 minutes to lick all of the marrow out, leaving the bone clean. The bone is uninteresting to them, too hard to gnaw.
When I lived in the suburbs I would toss the “clean” marrow bones in the garbage, but here in the country with a large lot it’s easier – and much less smelly – to hurl them over the fence into my field. Most of the year I don’t see the bones, hidden in the tall field grass or disappearing under the snow. Only during mud season – that short time after all the snow has melted but the new field grass has yet to grow – do I see all of the marrow bones I’ve tossed. A lot, over fifteen years! Thus my nickname for that section of my field: the bone yard.
What I saw on December 20th was one raven standing on and pecking at a marrow bone, the other pecking away at a different bone, probably the two I had tossed out there two days earlier.
I guess this is an example of a three-part symbiotic relationship: I purchase the marrow bones; the dogs eat their favorite part; I toss the “clean” bones over the fence where the ravens can make them truly clean. Sometimes the bones are cut so long that the boys can’t remove all of the marrow. I think the ravens have learned it’s worth checking them, just in case there’s any marrow left.
Finn is irritated by this new habit of the ravens. If he sees them through a window, he crashes out through the dog door, barking as he rushes the fence, causing the ravens to fly away.
Conall’s reaction to the ravens has been more subdued than Finn’s. Maybe his ancient wolf DNA tells him they’re friends, not foes. Yet the longer Finn reacts to ravens – or more precisely, over-reacts – the more inclined Conall is to join him, although more quietly and less urgently. Which is the reverse of what happens when they spy a fox in the field: Conall goes ballistic, while Finn might offer a bark or two but mostly ignores it.
If Finn is inside with me and Conall is alone in the yard, the ravens go about their business without harassment. Even when Conall challenges their presence, they ignore him.
Marrow bones are not the only reason the ravens are hanging about.
Conall is an excellent vole hunter. I knew this within days of bringing him home as an eight-week-old puppy and he caught one in the yard. Not liking the damage voles do to the grass in my yard, I praised him lavishly. Maybe too much, because until he was at least year old he would bring voles into the house through the dog door to show me, often still alive, seeking praise and validation for his hunting skills. I often wondered if Conall was part cat. If I tried to rescue the still-alive vole, Conall would quickly crunch and swallow it. Ugh!
Conall has continued to find and kill voles in the yard, although now – thankfully – he simply leaves them dead in the yard for me to find later when I’m pitching dog poop over the fence into the field. I’ve always hoped that the voles he kills and I toss into the field end up feeding some other animal, whether fox, coyote, turkey vulture or red-tailed hawk.
I hadn’t thought about ravens as part of that calculus.
I do now.
For whatever reason – population explosion in voles or prime conditions in snow on the ground or both – Conall has been finding more than the usual number of voles. I toss them all over the fence.
A few days ago, Conall found and killed two voles. I tossed them into the field. Because the snow had frozen hard over several cold, clear days, the voles remained on the surface where I could see them.
A day later, Conall caught another vole. It was early afternoon and I was inside. Through the window I saw the dead vole between Conall’s front paws as he rested on the snow in the yard. I called him inside to get both dogs ready for a walk down in the valley. From that same window I watched one of the ravens fly low over the field toward the house, eventually flying right over that part of the yard and the vole.
I wonder if the vole will still be in the yard when we get home?
Because we were only gone an hour or so, during daylight hours, the only creature I can imagine would access the yard to take the vole is a raven. Or maybe a red-tailed hawk.
I’m betting on the raven.
The two voles I’d tossed onto the snow in the field the day before were also gone.
I believe this is another example of our three-way symbiotic relationship – human, dog, raven – although I suppose I’m the least necessary part of the equation since it appears the ravens are willing to risk coming into the yard for a vole if they know we’ve left and the dogs won’t harass them. But I bet they appreciate that I toss them over the fence and into the field for easier access.
I also bet that the ravens wait and watch to see when my vehicle heads down my driveway, knowing from experience that the dogs are almost always with me, making the field and yard safe for their exploration.
Feature image: common raven; Pixabay.