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Avoidance of novel stimuli (neophobia) affects how wild animals interact with their environment and may partly determine whether animals persist in human-altered landscapes. The neuroendocrine mediators of neophobia are poorly understood, although past work demonstrated that experimentally reducing circulating corticosterone in wild-caught house sparrows (Passer domesticus) decreased neophobia toward novel objects placed near the food dish. In this experiment, we directly tested the role of one of the two types of corticosterone receptors, the glucocorticoid receptor (GR), in mediating neophobia in house sparrows by administering a GR antagonist (RU486, n = 10) or a vehicle control (peanut oil, n = 10) over 5 consecutive days and measuring responses to novel objects both pre- and post-treatment. We also measured baseline and stress-induced corticosterone in all sparrows on the final day of behavior trials. To better understand the effects of RU486 on corticosterone over time, in a separate group of sparrows (n = 12) we administered RU486 or vehicle over 5 days and took multiple blood samples to assess baseline and stress-induced corticosterone. Overall, we did not detect an effect of subcutaneous RU486 injections on neophobia behavior. However, we did find that RU486 injections significantly decreased stress-induced corticosterone levels starting 1 day post-injection and baseline corticosterone levels starting 6 days post-injection, compared to vehicle-injected controls. Our results suggest that GR is not involved in mediating neophobia behavior in house sparrows.
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Conspecific alarm calls prevent the attenuation of neophobia behavior in wild-caught house sparrows (Passer domesticus)
Some individuals respond to new objects, foods, or environments with wariness (neophobia), whereas others are willing to approach and explore. Because novel stimuli can represent both dangers and resources, group-living species may show adaptive plasticity in neophobia in response to social cues. To better understand how conspecific calls can influence neophobia in a highly gregarious species, we exposed individual house sparrows (Passer domesticus) to either conspecific alarm calls (n = 12), conspecific contact calls (n = 12), or no playback (n = 12) and measured latency to feed in the presence of novel objects. We also measured novelty responses with no sound the week before and after the sound treatment week for all individuals. Relative to no playback and contact calls, we predicted that conspecific alarm calls would increase neophobia behavior during the acoustic trial and that these effects would persist the week after exposure. Instead, we found that individuals in the contact call and no playback groups became less neophobic as weeks progressed, while the alarm call group showed no attenuation of neophobia. There was a significant interaction between week and treatment, where neophobia responses over the three weeks were significantly different for individuals exposed to alarm calls compared to the contact and no playback groups combined. These results suggest that house sparrows learn social information about potentially threatening stimuli from conspecific alarm calls; here, that novel objects may be dangerous.
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- Award ID(s):
- 2237423
- PAR ID:
- 10575502
- Publisher / Repository:
- Frontiers in Bird Science
- Date Published:
- Journal Name:
- Frontiers in Bird Science
- Volume:
- 3
- ISSN:
- 2813-3870
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Neophobia is a behavior characterized by a reluctance to approach novel objects. We measured neophobia in captive wild house sparrows (Passer domesticus) by comparing the time it took for hungry birds to approach their normal food dish compared to one that had been modified with a novel object. We tested the behavior of animals captured at different times of year to test for seasonal variation in neophobia. One group of birds tested in July approached their food dishes much more quickly than all other birds (a matter of seconds rather than minutes whether or not there was a novel object), a response that was not repeated in a subsequent July. When this possible outlier group was removed from the analysis, approach times to novel objects were not affected by season. However, animals captured and tested in October had a stronger motivation to feed (i.e., they approached unmodified food dishes faster) than birds captured at other times of the year. If we define “neophobia” as an increase in latency to approach a novel versus an unmodified food dish, then there is little evidence for underlying seasonal variation in risk assessment, although a general motivation to feed does show a seasonal pattern.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/fbirs.2024.1440063
