The previous post that a parasite triggers wolves to become courageous leaders may sound fantastic, but something difficult to accept as a fact. If you recall rule number one of statistics: “correlations are not causations”, you may realise that there could be other explanations to understand wolves’ the peculiar behaviour of some wolves who happened to have been infected.
What if the same behaviour, aggression, tendencies to walk out of the pack, and courage is the reason that caused the disease in the first place? The claim is not entirely without reason, as the animal gets the illness from cougars that share the same land space. After all, these are observational studies. Naturally, we would have liked to see results from a controlled study.
The researchers selected 64 laboratory rats and infected 32 of them (experimental group) with a cyst-forming strain of the parasite. The other 32 are given a placebo (control group). The rates were exposed to an area, and its corners contained distinct odours, representing four species – rat, cat, rabbit and neutral.
Now, a bit of evolution. Small mammals under heavy predation pressure evolved as species that could identify and avoid the presence of their predators. For rats, it is the ability to smell and avoid cats. You know already that it is not a rat that decided to build the capability to help itself; rather, as per the principle of survival of the fittest, only those rat species survived and had multitudes of offspring. Studies have shown that rats don’t lose the anti-predator behaviour (aversion to cat smell) even after hundreds of generations without having felt the presence of a cat.
And this is where our study got interesting. In the experiment, the status of the rats, infected or otherwise, did not change their movement towards the three non-cat selling areas. Whereas the uninfected rate disproportionally avoided cat-smelling spots compared to the infected.
References
- Fatal attraction in rats infected with Toxoplasma gondii: Proc. R. Soc. Lond
- Fatal attraction: Nature
- Meyer et al., 5 (1180), 2022: Communications Biology
- Parasite gives wolves what it takes to be pack leaders: Nature
- Fatal attraction in rats infected with Toxoplasma gondii: Proc Biol Sci.
