Fine‐scale diet of the Australian sea lion (Neophoca cinerea) using DNA‐based analysis of faeces

Abstract

We applied DNA-based faecal analysis to determine the diet of female Australian sea lions (n = 12) from two breeding colonies in South Australia. DNA dietary components of fish and cephalopods were amplified using the polymerase chain reaction and mitochondrial DNA primers targeting the short (~100 base pair) section of the 16S gene region. Prey diversity was determined by sequencing~50 amplicons generated from clone libraries developed for each individual. Faecal DNA was also combined and cloned from multiple individuals at each colony and fish diversity determined. Diets varied between individuals and sites. Overall, DNA analysis identified a broad diversity of prey comprising 23 fish and five cephalopod taxa, including many species not previously described as prey of the Australian sea lion. Labridae (wrasse), Monacanthidae (leatherjackets) and Mullidae (goat fish) were important fish prey taxa. Commonly identified cephalopods were Octopodidae (octopus), Loliginidae (calamary squid) and Sepiidae (cuttlefish). Comparisons of fish prey diversity determined by pooling faecal DNA from several samples provided a reasonable but incomplete resemblance (55-71%) to the total fish diversity identified across individual diets at each site. Interpretation of diet based on the recovery of prey hard-parts identified one cephalopod beak (Octopus sp.) and one fish otolith (Parapriacanthus elongatus). The present study highlights the value of DNA-based analyses and their capabilities to enhance information of trophic interactions.

Chew, shake, and tear: Prey processing in Australian sea lions (Neophoca cinerea)

“…, Peters et al . ), are similar in size, and share very similar craniodental morphology (Ling ). Captive and wild Australian fur seals have been observed using shake feeding, but not “hold and tear” feeding methods to process their prey (Hocking et al .…”

“…This is of interest when we compare the processing methods used by this species with those used by another Australian otariid, the Australian fur seal. Both species are benthic foragers that target a wide selection of prey types (Deagle et al 2009, Peters et al 2015, are similar in size, and share very similar craniodental morphology (Ling 1992). Captive and wild Australian fur seals have been observed using shake feeding, but not "hold and tear" feeding methods to process their prey (Hocking et al 2016).…”

“…We used prey species that were similar to species that sea lions targeted in the wild (Peters et al . ). Prey species chosen was dependent on availability at the local fish market near each institution.…”

“…In some events it was possible to use two cameras, with one placed below the water and one above. We used prey species that were similar to species that sea lions targeted in the wild (Peters et al 2015). Prey species chosen was dependent on availability at the local fish market near each institution.…”

Large‐scale molecular diet analysis in a generalist marine mammal reveals male preference for prey of conservation concern

“…In this study, we performed DNA-bar coding analysis and qPCR on harbor seal fecal samples to determine the identity, estimate prey species proportions in diet, and the sex of the harbor seal, respectively. Other pinniped studies have used molecular techniques to determine the diet of one sex (Jeanniard-du-Dot et al, 2017;Peters et al, 2015) or the diet of the species without differentiating the sex (Hui, Morita, Kobayashi, Mitani, & Miyashita, 2017;Kvitrud, Riemer, Brown, Bellinger, & Banks, 2005;Parsons, Piertney, Middlemas, Hammond, & Armstrong, 2005;Thomas et al, 2017;Wright, Riemer, Brown, Ougzin, & Bucklin, 2007). To our knowledge, this is the first study in pinnipeds that incorporates these two molecular methods to differentiate males and females and estimate their diet from scat.…”