Rising global temperatures in the Arctic region is causing morbid behaviors in nature. Researchers working in Alaska discovered that female wolf spiders are turning into cannibalism in order to survive.
The researchers found these animals eating juvenile spiders which resulted in a decrease in their population in certain areas. This happens because of the warming weather that causes spiders becoming larger and producing more offspring, which creates more competition for resources.
Increased population causes increased competition for resources
Researchers from Washington University first observed the cannibalistic behavior of wolf spiders while they were working at two sites in the Alaskan Arctic.
The first author in the study and post-doctoral fellow in biology in Arts & Sciences, Amanda Koltz, said that their field and experimental data suggest that when there are lots of spiders around, wolf spiders turn to cannibalism more frequently even though it is not the best dietary choice for them.
It is likely a reflection of increased competition among the spiders for resources, Koltz said.
As many animals regulate their body temperature are known to experience changes in a warming environment, previous studies on wolf spiders suggest that they too have been generally affected in the Arctic region as climate change causes the summer season to grow longer.
The critical question remains now is whether this change actually results in more spiders in the wild. Koltz noted that resources and space on the tundra are limited.
A shift of diet to cannibalism
While doing their research, Koltz and her team compared the observations in Alaska with another separate experiment that manipulated the number of wolf spiders in an enclosed area. It allowed them to observe how the diet of the wolf spider is affected when living in higher spider densities.
Koltz determined after an analysis of the arachnids in the study that the presence of larger female spiders meant there were fewer young spiders. This result is surprising as one usually assumes that the presence of larger spiders means there would be more offspring because they produce more young.
The researchers used stable isotope analysis and found that the spiders at the site with larger female spiders had different diets than at the site with smaller females.
Their observations suggest that where spiders were larger and reproduction is likely higher, spiders cannibalized each other more often. The dietary shift of the spiders was consistent with that of a change toward cannibalism would look. Experimental data further supported this idea.
Koltz said that "wolf spiders that were experimentally exposed to higher densities underwent a dietary shift similar to that of the field population where females were bigger-and where we would expect competition and cannibalism among wolf spiders to be highest."
The research is the first to determine that cannibalism regulates population among the spiders, although it is commonly seen among wolf spiders in the wild.
Moreover, cannibalism on other species of spiders reduces competition as population also decreases. Evidence from other studies suggests that wolf spiders that are only fed with other wolf spiders tend not to live longer than those who have a more varied diet.
It means that bigger spiders may not always lead to more spiders on the landscape even if these spiders reproduce more.
Although the experiment is based in the Arctic, the primary purpose of their study is not limited to the area or potentially even to wolf spiders. The results are a reminder that changes in invertebrate body size due to climate change could have widespread ecological consequences in intraspecific competition, diet, and population structure.
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