Recall the other week my grumbling about a BBC report which implied via its choice of words that squirrels were better communicators than humans? Well this week, the BBC reports (in an article concerning symbiosis between hornbills and warthogs) that "banded mongooses remove ticks from warthogs, in what is believed by scientists to be the only symbiotic relationship between two mammal species."
Really? So is it that humans aren't mammals, or that the relationships between cats, dogs, rabbits, hamsters, gerbils, rats etc and humans aren't symbiotic, despite the fact that both parties benefit? The non-human gets food and care, the human gets companionship (and with it, superior health and longevity). Looks like a form of symbiosis to me. Perhaps they just missed out the phrase "...in the wild"?
But of course, domestic cats and dogs originate from symbiotic relationships between their wild ancestors and humans; all modern dog breeds are descended from wolves that are believed to have lived symbiotically on the edge of human settlements. Symbiosis between cats and humans is believed to have originated in Egypt where grain storage lead to plagues of rodents that created an opportunity for symbiosis that still persists today.
Besides, there are several other instances of symbiosis between mammal species in the wild - one of which was even reported by a BBC nature documentary. Beavers are willing to share their lodge with other mammals; the other mammal brings in some food to "pay" for the lodgings, but this is still essentially a symbiotic relationship. Some naturalists report muskrats and beavers frequently share lodges in winter, a clear example of mammals of different species co-operating.
The point isn't that mammal-mammal symbiosis is rare, but rather that bird-mammal symbiosis is incredibly common. There are huge number of bird and mammal species that co-operate either in grooming rituals (such as one between the warthog and the hornbill mentioned above), alarm calling (as with antelope and Hartlaub's ducks, or red squirrels and jays), or mutual foraging (as with jacanas and gorillas, or egrets and elephants). Neither is inter-class co-operation restricted to birds-with-mammals; dolphins have been known to co-operate with sharks in order to corral fish - a relationship that connects species separated by 400 million years of divergence.
The point is that, once again, an anthropocentric viewpoint obfuscates the facts being reported: the BBC reporter who wrote the article didn't think twice about the claim that mammal-mammal symbiosis was rare, not once it was validated by nebulous "scientists". Yet humans are mammals, and we live symbiotically with a huge number of species - both as pets, and in many other contexts besides. If one is willing to count the conservationist's feeling of elevation when they act to preserve a species under threat as their "gain" in a symbiotic relationship with an animal being protected, the entire field of nature conservation falls under the remit of mutual benefit between animal species.