After introduction, the closely-related house sparrow and Eurasian tree sparrow have had varying degrees of invasion success. Whereas the Eurasian tree sparrow is found in a limited region, the house sparrow is much more broadly-distributed across North America.
News — What makes a good invader? Two closely related sparrows were intentionally introduced to the US in the mid-1800s. One, the house sparrow, was quite successful and has since exploded, now ranging throughout the US. The Eurasian tree sparrow, on the other hand, had comparatively mediocre success.
On paper these sparrows appear to be quite similar, so what then explains the difference in success between these two species?
Although environmental and ecological factors cannot be ignored, Dr. Christine Lattin, an Assistant Professor in Louisiana State University’s Biological Sciences Department, believes behavior may play a larger, understudied role in the success of invasive species. “If we really want a complete picture of what makes a good invader, we have to look at the whole spectrum of traits that might help animals be successful to the exclusion of other species”, explains Lattin.
In particular, Lattin and colleagues investigated neophobia, an aversion towards novelty, as a potential driver of invasion success. This group quantified differences in behavior towards novel objects, novel foods, and the ability to habituate to repeated exposures of the same initially novel object in Eurasian tree sparrows. To provide a close comparison between the two sparrows, researchers used the same methods as an earlier study by Kimball et al. (2022) investigating neophobia in house sparrows. Given the difference in invasion success, Lattin and her co-authors hypothesized the tree sparrows would be more neophobic towards novel objects and novel foods, as well as slower to habituate to novel objects than house sparrows. Results of this study showed no difference in initial responses to novel objects, but that Eurasian tree sparrows were less likely to try new foods like grated cheese and took longer to habituate to novel objects like a purple, plastic Easter egg. However, individual responses to novel objects and foods were often correlated in both species. In other words, sparrows that were willing to try novel foods were also faster to approach novel objects.
Invaders must quickly and successfully adjust to new environments, and this study suggests neophobia could be a factor in that success. However, Lattin indicates neophobia could also play a major role in future species’ survival in a changing environment. “An animal’s response to new things in its environment really has the potential to not just teach us about invasion success, but also about the ability of animals to live in human-altered environments,” Lattin explains. “It is important to understand which species will be able to live in an environment that’s full of novelty.” Future research looks to measure neophobia in a broader sampling of birds.
Lattin will present this work during the Society for Integrative and Comparative Biology’s Annual Meeting in January 2024 in Seattle, Washington.
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