| 1. |
- Greenberg, Larry, 1955-, et al.
(författare)
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Body shape and fin size in juvenile Atlantic salmon (Salmo salar) : effects of temperature during embryogenesis
- 2021
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Ingår i: Canadian Journal of Zoology. - : CANADIAN SCIENCE PUBLISHING. - 0008-4301 .- 1480-3283. ; 99:5, s. 381-389
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Tidskriftsartikel (refereegranskat)abstract
- Temperature during egg incubation and early development influences later life stages of fishes, potentially influencing survival. Throughout its distribution, Atlantic salmon (Salmo salar Linnaeus, 1758) have experienced population declines, and in view of ongoing global warming, we tested if temperature during the earliest developmental stages modified body shape and fin size when temperatures averaged 2.6 vs. 5.6 degrees C. This temperature difference simulates increases predicted in climate change scenarios. Based on previous studies, we hypothesized that salmon originating from eggs subjected to cold incubation temperatures would have slimmer bodies and larger pectoral and dorsal fins than salmon from eggs that experienced warmer temperatures. After hatching, the juveniles were raised for 1 year under identical temperatures, after which we measured their body shape and fin areas. We found no support for our hypothesis regarding body shape. Indeed, we found the opposite, with cold-incubated salmon having deeper bodies than warm-incubated salmon. For fin size, the pectoral fins of cold-incubated salmon were larger than for warm-incubated salmon as predicted, but there was no difference in dorsal fin size. These results suggest that global warming may lead to altered body shape and fin size, possibly affecting swimming performance, and thus raise questions about the ecological consequences of the changes.
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| 2. |
- Ortiz, Sara Torres, et al.
(författare)
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Group hunting in harbour porpoises (Phocoena phocoena)
- 2021
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Ingår i: Canadian Journal of Zoology. - : Canadian Science Publishing. - 0008-4301 .- 1480-3283. ; 99:6, s. 511-520
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Tidskriftsartikel (refereegranskat)abstract
- Cooperative hunting involves individual predators relating in time and space to each other’s actions to more efficiently track down and catch prey. The evolution of advanced cognitive abilities and sociality in animals are strongly associated with cooperative hunting abilities as has been shown in lions, chimpanzees, and dolphins. Much less is known about cooperative hunting in seemingly unsocial animals, such as the harbour porpoise (Phocoena phocoena (Linnaeus, 1758)). Using drones, we were able to record 159 hunting sequences of porpoises, out of which 95 sequences involved more than one porpoise. To better understand if the harbour porpoises were individually attracted by the fish school or formed an organized hunting strategy, the behaviour of each individual porpoise in relation to the targeted fish school was analysed. The results indicate role specialization, which is considered the most sophisticated form of collaborative hunting and only rarely seen in animals. Our study challenges previous knowledge about harbour porpoises and opens up for the possibility of other seemingly non-social species employing sophisticated collaborative hunting methods.
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| 3. |
- Rydell, J., et al.
(författare)
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White and clear wings in bats (Chiroptera)
- 2020
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Ingår i: Canadian Journal of Zoology. - : Canadian Science Publishing. - 0008-4301 .- 1480-3283. ; 98:2, s. 149-156
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Tidskriftsartikel (refereegranskat)abstract
- White or clear (“whitish”) wings are a distinct feature in about 30 species of tropical insectivorous bats (Mammalia: Chiroptera) belonging to three families (Emballonuridae, Molossidae, and Vespertilionidae). Such wings may provide camouflage against the sky at dusk and dawn, when bats commute to and from the roost and are vulnerable to aerial predation from birds. We tested this hypothesis by comparing the contrast of black, white, and transparent plastic models against the evening sky. Compared with normally dark wings, white and particularly transparent wings indeed reduce the contrast against the sky and may also prevent overheating in bats flying in daylight. Whitish wings could facilitate earlier evening emergence and later morning return, increasing access to crepuscular or diurnal insects as food. But whitish wings become maladaptive near artificial lights, where they are highly visible when illuminated against the dark sky. Pale but colored (not whitish) wings and reticulated patterns on translucent wings in some African and south Asian bats may be variations on the same theme, functional as camouflage against a lit background of vegetation and shades.
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