Abstract
Variation in the diet of generalist insectivores can be affected by site‐specific traits including weather, habitat, and season, as well as demographic traits such as reproductive status and age. We used molecular methods to compare diets of three distinct New Zealand populations of lesser short‐tailed bats, Mystacina tuberculata. Summer diets were compared between a southern cold‐temperate (Eglinton) and a northern population (Puroera). Winter diets were compared between Pureora and a subtropical offshore island population (Hauturu). This also permitted seasonal diet comparisons within the Pureora population. Lepidoptera and Diptera accounted for >80% of MOTUs identified from fecal matter at each site/season. The proportion of orders represented within prey and the Simpson diversity index, differed between sites and seasons within the Pureora population. For the Pureora population, the value of the Simpson diversity index was higher in summer than winter and was higher in Pureora compared to Eglinton. Summer Eglinton samples revealed that juvenile diets appeared to be more diverse than other demographic groups. Lactating females had the lowest dietary diversity during summer in Pureora. In Hauturu, we found a significant negative relationship between mean ambient temperature and prey richness. Our data suggest that M. tuberculata incorporate a narrower diversity of terrestrial insects than previously reported. This provides novel insights into foraging behavior and ecological interactions within different habitats. Our study is the first from the Southern Hemisphere to use molecular techniques to examine spatiotemporal variation in the diet of a generalist insectivore that inhabits a contiguous range with several habitat types and climates.
Highlights
Our study was conducted at three sites: (a) the Pikiariki Ecological Area of Pureora Forest Park (Pureora; 38°26′S, 175°39′E), central North Island, New Zealand, during January 2014–April 2015 (Pureora summer) and May–July 2015 (Pureora winter); (b) the Eglinton Valley of Fiordland National Park (Eglinton; 44°58′S, 168°00′E), South Island, New Zealand, during January–April 2016 (Eglinton); and (c) Hauturu/Little Barrier Island (Hauturu), 80 km off the east coast of the North Island, New Zealand, during May–July 2016 (Hauturu)
Our study is one of the first to use molecular techniques to examine spatiotemporal variation in the diet of a generalist insectivore that inhabits a contiguous range with several habitat types and climates
We found that prey orders consumed differed between winter and summer sites as well as seasonally and that diversity was higher in summer compared to winter
Summary
Individuals must balance energetic transactions (i.e., energy spent vs. energy gained). Foraging is an expenditure, it is the source of energy gain. An individual’s energy balance is influenced by biotic and abiotic factors such as photoperiod, food/ water availability, digestibility and abundance of prey, and ambient temperature (Ta) (Doucette, Brigham, Pavey, & Geiser, 2012; Körtner & Geiser, 2000; McNab, 2002; Song & Geiser, 1997). Endotherms (i.e., most mammals and birds) face a heavy energetic burden, as the majority of their output is lost as metabolic heat maintaining normothermic body temperatures. Due to surface to volume ratio laws, active small insectivorous endotherms are likely under even greater pressures during winter than sized herbivorous species, as insect populations are more sensitive to weather. Many volant insects have limited flight capacities, cannot fly, or are dormant at low Ta (Jones, Duvergé, & Ransome, 1995)
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