Abstract
Leopard seals (Hydrurga leptonyx) are top-order predators that prey on a wide variety of species including crustaceans, cephalopods, fishes, birds, and pinnipeds. While multiple diet studies have been conducted worldwide, there are no previous accounts of leopard seals predating on chondrichthyans. As part of a wider study on the diet of leopard seals in New Zealand (NZ) waters, researchers and citizen scientists recorded 39 observations of predation and collected 127 scats (166 total records) between 1942 and 2019. Predation on chondrichthyans was detected in 23.1% (n = 9) of observations of predation and 7.1% (n = 9) of scats (the latter via morphological examination and DNA sequencing). From both observations of predations and scats, three chondrichthyan species or genus were identified; elephantfish (Callorhinchus milii), ghost sharks (Hydrolagus spp.) and spiny dogfish (Squalus acanthias). While this is the first published record of leopard seals feeding on chondrichthyans, the relatively high frequency of occurrence within our NZ records, and that certain individuals appeared to target this type of prey, indicates that these species could constitute a substantial, or important, part of the diet for some leopard seals in this region. As chondrichthyans form an important part of the NZ marine ecosystems, our recognition of an additional top-order predator of these species contributes to understanding the overall health of, and future impacts of predators on, the wider NZ marine ecosystem.
Highlights
Leopard seals (Hydrurga leptonyx) are large, top-order predators that have a typical circumpolar distribution and are locally abundant between 50◦ and 80◦ S (Riedman, 1990; Casaux et al, 2009)
Data was divided into two main categories: (1) ‘observations of predation’, which included visual observations and evidence of leopard seals consuming or caching prey and (2) ‘scat remains’ which included non-fecal material that was not digested recovered from scats
Of the 39 observations of predation, 23.1% (n = 9) documented leopard seals feeding on chondrichthyans
Summary
Leopard seals (Hydrurga leptonyx) are large, top-order predators that have a typical circumpolar distribution and are locally abundant between 50◦ and 80◦ S (Riedman, 1990; Casaux et al, 2009). Frontiers in Marine Science | www.frontiersin.org van der Linde et al. Leopard Seals Predating on Chondrichthyans include Adélie penguins (Pygoscelis adeliae) and crabeater seals (Lobodon carcinophagus) (Siniff and Stone, 1985)], there is the potential that leopard seals can affect marine ecosystems through competition with sympatric mesopredators (e.g., Cupples et al, 2011) or perceived predation risk which can reduce mesopredator fitness (e.g., Gigliotti et al, 2020). Leopard Seals Predating on Chondrichthyans include Adélie penguins (Pygoscelis adeliae) and crabeater seals (Lobodon carcinophagus) (Siniff and Stone, 1985)], there is the potential that leopard seals can affect marine ecosystems through competition with sympatric mesopredators (e.g., Cupples et al, 2011) or perceived predation risk which can reduce mesopredator fitness (e.g., Gigliotti et al, 2020) Despite these potential ecosystem effects, even today we still have a “poor understanding of [leopard seal] foraging ecology” (Krause et al, 2020)
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