An international team from universities in Belgium and Italy used a natural experiment with populations of native red squirrels (Sciurus vulgaris) living with extraterrestrial gray squirrels (Sciurus carolinensis) to study the effects of a parasitic helminth (worm), that of gray squirrels. Strongyloides robustus is transmitted through the personality of native squirrels.

By comparing repeated measurements of squirrel parasite infection and personality with those taken in locations where only native species were present, they showed that exotic parasite infection caused a significant decrease in squirrel activity and changed their relationship with native parasites.

Squirrels usually only wear one type of gastrointestinal helmet (Trypanoxyuris sciuri) co-evolved with this arboreal mammal; As a result, they can be sensitive to the spread of parasites, acquiring new species of parasites that are transmitted from another host, in this case, the exotic gray squirrel. Protect you family and your home by getting squirrel control from experts. Gray squirrels in Italy are typically home to Strongyloides robustus, an introduced helminth from their native range that they transfer to native red squirrels.

In her study, Dr. Francesca Santicchia and her co-author’s negative correlations between squirrel activity and infection with the alien parasite S. robustus at sites invaded by gray squirrels. The activity was also negatively correlated with the condition by its native helminth (T. sciuri), but only when gray squirrels were present, not in the red spots. In addition, individuals who acquired S. robustus during the study reduced its post-infection activity, while non-infected animals did not.

Their results, showing that parasite-mediated competition is energetically costly and can disrupt “normal” relationships between native host and parasite, are published today in the Journal of Animal Ecology. This new publication comes two years after researchers’ earlier discovery that gray squirrels cause increased stress hormone levels in coexisting red squirrels, published in the same journal.

“It is well known that our squirrel is threatened with extinction due to the introduction of a ‘foreign’ species but that one of the mechanisms involved is decreased activity, a personality trait that tends to be related to the intensity or efficiency of foraging caused by a parasitic helminth that spreads from gray squirrels, is a recent find.”

“This spill is very similar to what happens with the squirrel pox virus in the UK and Ireland,” adds Dr. Claudia Romeo and Dr. Nicola Ferrari from the University of Milan added, “although, in this case of an endoparasite spill, the effect is more subtle and  it does not lead directly to the execution of the animal.”

In this study, the researchers provided compelling evidence that the spread of the alien helminth to naive red squirrels leads to decreased activity, a behavior that requires high energy expenditure, and relationships between squirrels.

“This is a form of parasite-mediated competition that can intensify the effects of interspecific competition with gray squirrels for foods such as coniferous, hazelnut, or chestnut seeds,” emphasize Wauters and Romeo.

The decreased activity could lead to a decrease in food intake and, together with a chronic increase in glucocorticoid levels, could lead to reduced body growth or reproductive success or even decreased the survival of red squirrels that are forced to close their habitat. With the invaders share. Combining these interactive ecological and physiological processes will lead to the extinction of the squirrel population in just a few years.