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Human settlements and urbanisation are increasing globally, with more than half of the Earth's terrestrial surface being impacted by humans. This development has resulted in numerous anthropogenic stressors including nocturnal sensory pollution (i.e. light pollution), which is a key driver of insect declines. Nocturnality is hypothesized to reduce predation risk from visually-guided diurnal predators. More than half of all insect species, and 80% of Lepidoptera, are estimated to be nocturnal. Predation rates on insects are likely a result of habitat, time of day and the local predator composition. We investigated how predation rates on plasticine moth replicas differed between urban and rural sites, and between night and day. Visually matching paper-winged, clay-bodied replicas of the white-lined sphinx moth, Hyles lineata, were placed in a natural area within the city of El Paso, Texas, and in remote Chihuahuan Desert with minimal human disturbance. These replicas were checked during dawn and dusk for 3 days. Predation rates were significantly lower at night than during the day regardless of location, and predator composition differed between sites. Insectivorous birds were the primary diurnal predators in both locations, whereas nocturnal predators were represented primarily by insects at the rural site and by mammals at the urban site. These findings support the hypothesis that visually-guided predators, such as birds, exert higher predation pressures during the day, and supports the hypothesis that insect biodiversity, especially of predaceous insects, is affected by urbanisation.
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A survey of nocturnality and risk for savanna chimpanzees at Assirik, Senegal
Abstract Chimpanzees (Pan troglodytes) in Senegal may use nocturnality to mitigate hyperthermia risk in semi-arid environments but the degree of nocturnality for such chimpanzees also in sympatry with large carnivores remains uncertain. We compared diel activity among chimpanzees and their potential predators at Assirik in Niokolo-Koba National Park and contextualized these findings relative to other unit-groups in savanna landscapes. From 2015-2018, we generated a predator inventory using multi-modal methods and monitored the diel activity of chimpanzees and predators with camera traps [camera trap (CT) days]. From 2015-2023, we also surveyed for evidence of predation during recce walks. Six potential nonhuman predators occur at Assirik, including lions (Panthera leo), leopards (Panthera pardus), spotted hyenas (Crocuta crocuta), African wild dogs (Lycaon pictus), Nile crocodiles (Crocodylus niloticus), and rock pythons (Python sebae). We documented one suspected case of a predator killing a chimpanzee. Nocturnality comprised 12.7% of CT events for chimpanzees and these events were more concentrated at twilight. Chimpanzees were more active during the day, predators were more active at night, and there was substantial temporal overlap among chimpanzees and potential predators during twilight intervals. Our findings support the hypothesis that savanna chimpanzees in Senegal are active at night in response to the extremely hot environment. We hypothesize that Assirik chimpanzees experience a tension between decreasing hyperthermia and increasing predation risk during nocturnality.
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- Award ID(s):
- 1700313
- PAR ID:
- 10556952
- Publisher / Repository:
- Brill
- Date Published:
- Journal Name:
- Folia Primatologica
- Volume:
- 95
- Issue:
- 3
- ISSN:
- 0015-5713
- Page Range / eLocation ID:
- 191 to 210
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1163/14219980-bja10032
