In a recent study done by scientists from the University of Alberta, it was found that male red squirrels kill the baby squirrels of their male rivals in times when there is an abundance of food. The study was published in the Ecology journal and it is the first ever proof of the eccentric practice of the spirited rodents.
Red Squirrels: What Are They?
Also called the Eurasian red squirrel, the red squirrel is an omnivorous rodent that is prevalent in North America, Italy, Ireland, and Great Britain. Due to habitat loss, its population has declined drastically in the past few years.
Its most distinguishable feature is its sharp, curved claws, which allow it to climb up the trees and jump over think branches. It also has a long tail that helps it balance while jumping and running from tree to tree and keeps it warm while sleeping.
This creature sheds its coat two times a year. When summer is near, it switches to a thinner coat. During winter, it changes to a dark and thicker coat.
The Beginning of the Study
Jessica Haines, a biologist and a post-doctoral student, said that the result of the study was indeed surprising. Though it was a bit horrifying, it was a bit fascinating and interesting to have discovered such odd behavior.
Haines personally witnessed such behavior in 2014 while doing field work on red squirrels near Kluane National Park. The behavior is termed sexually selected infanticide.
How It All Began
She recalled what had happened. She said she heard a bit of a commotion near her so she decided to look over. That was when she saw the odd event. It just happened so fast. Her curiosity made her decide to conduct a further study.
She started tagging the ears of some squirrels using distinct markers. That way, she could easily identify which squirrels were involved. At one moment, she saw a male squirrel enter the territory of the females. It immediately grabbed a pup and bit its stomach and chest, killing it instantly. After that, the male squirrel was chased by the mother, making it decide to drop the deceased pup.
Male Rivalry at Its Finest
Haines could not right and there conclude if the male squirrel was the father of the pups, the reason why genetic techniques and strategies were performed. After several tests, it was found that the male squirrel that killed the pup was not the father.
At that time, Haines concluded that the male squirrel killed the offspring of his rival. Later on that year, it was already the father of the female squirrel’s new set of offspring. By killing the pup, it had an advantage over its rival.
In the later part of the study, it was also found that female squirrels can breed quickly if their first set of litter is killed. When a female squirrel’s litter dies, she’s more likely to have another batch. Otherwise, she’d less likely have another offspring.
The Killing of Offspring Is Common During Mast Years
The study was done during those years when there was an abundance of white spruce cones – the primary food source of squirrels. These trees are known to produce vast amounts of cones annually. But there are also years when they produce cones periodically. These years are called the “mast years”.
Interestingly, squirrels can tell when these mast years will happen. During these years, which happen rarely, female squirrels usually have two litters.
The Surprising Conclusion
Haines then concluded that infanticide happens frequently during the mast years because it is the time when female squirrels are likely to give birth to another set of litter. During other years, they don’t usually produce another litter, hence she thinks male squirrels won’t spend much time and energy killing the offspring. After all, they would not benefit from doing it.
Then again, during the mast years, the survival rate of red squirrel pups is still high despite the death of the first batch of pups. Also, sexually selected infanticide is rampant only among animals that live in groups, including grizzly bears and lions. Like red squirrels, lions kill the babies of their rivals before they can lead the pride.