Just as war drives the development of new technologies and weapons in the human world, the evolutionary arms race between predator and prey species causes both to constantly update their biological arsenals. The amazing precision of this natural weaponry is revealed in a new study that illustrates how rattlesnakes tailor their venom to ensure it is as lethal as possible to the squirrels living in their immediate neighborhood.
The results of this research which appears in the Proceedings of the Royal Society B are intriguing for several reasons. Firstly, the fact that so much variation exists within rattlesnake venom has major implications for people who get bitten by these sneaky slitherers, as standard anti-venoms may not necessary work for all snake bites.
Furthermore, the findings provide a fascinating insight into the evolutionary processes driving the perpetual deadly contest between these rattlesnakes and their squirrel prey.
To conduct their research, the study authors gathered venom from rattlesnakes in 12 different California locations, while also taking blood samples from the squirrels living in each of these vicinities. In the lab, they observed what happened when each venom was placed in contact with the blood serum of each of these squirrel populations.
As part of their defense mechanism against thesenatural predators, squirrels have developed resistance factors that prevent snake venom metalloproteinases (SVMP) from taking effect. SVMP breaks down connective tissue in order to enable the venom to penetrate vital organs.
Results showed that the snake venom was up to three times more effective when pitted against the blood of a squirrel that lived in the same immediate habitat. As such, the researchers suggest that as the squirrels develop resistance to the venom of nearby snakes, these snakes then up their game by evolving new weaponry to overcome this resistance.
It’s like resistance is a lock and venom is the key and I have to have the right key to open my office and another one to open the office next door, explained study co-author Matthew Holding. You could drive 20, 30 miles down the road and find a lot of variation in the venom and our research suggests that this variation is adapted to overcoming differences in squirrel venom resistance.
Intriguingly, squirrels living at higher altitudes were found to be less resistant to the venom of local rattlesnakes. Michael Meshcheryakov/Shutterstock
While theres nothing unusual about the fact that squirrels and snakes are in an evolutionary arms race with one another, the surprising thing is that in this case, the predators appear to be winning. Since the cost of being eaten is obviously much higher than the cost of missing a meal, it would make sense for prey species to hold the upper hand over their predators if both are to survive.
Exactly how the snakes have ended up with the advantage in this lethal game of one-upmanship is something that the researchers are currently unable to answer, yet their data suggests that there may be a surprising connection between altitude and venom resistance: squirrels living at higher elevations were found to be less resistant to the venom of their neighboring snakes.
Whatever the secret to the snakes success, its clear theyre packing some serious heat, which is bad news for the squirrels of California.
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