Protected area use by two sympatric marine predators repopulating their historical range

Abstract

As large carnivores recover from over-exploitation, managers often lack evidence-based information on species habitat requirements and the efficacy of management practices, particularly where species repopulate areas from which they have long been extirpated. We investigated the movement and habitat use by 2 semi-aquatic carnivores (Australian fur seals Arctocephalus pusillus doriferus and New Zealand fur seals A. forsteri) at the northern end of their distributions in Australia, where after a long absence both are recolonising their historic range. We also assessed male fur seal habitat use overlap with terrestrial and marine protected areas (PAs). While at the margin of the range during winter and early spring, the males remained inshore close to terrestrial sites and where interactions with humans often occur. From early spring, the males from the range margin showed uniform movement toward colonies in the core of the species’ range prior to their breeding seasons. This contrasts with males tracked from the core of the species’ range that returned periodically to colonies during the year, and highlights the importance of range-wide monitoring of a species to inform conservation planning. Habitat use by some males included over 90% of a marine PA at the margin of the species’ range. Most terrestrial haul-outs used were within terrestrial PAs, while sites not protected were on the margin of the range. Despite wide-ranging habits, their dependence on coastal sites, where human access and activities can be regulated and more readily enforced, suggests that terrestrial and marine PAs will continue to play an important role in managing the recovery of these fur seals.

Residency, movement patterns, behavior and demographics of reef manta rays in Komodo National Park

“…Until recently, manta rays (mostly reported as M. birostris , although some data predate the Marshall, Compagno & Bennett (2009) species redescription, and few reports of M. alfredi ) were actively targeted in fisheries <400 km to the east and west of the Komodo NP ( White et al, 2006 ; Heinrichs et al, 2011 ; Lewis et al, 2015 ). These fisheries suggest that additional adjacent manta ray aggregations exist or might become more apparent as populations recover, as observed with other marine species ( Pierszalowski et al, 2016 ; Salton et al, 2021 ). However, given the manta rays’ conservative life-history traits, local scale repopulation and spillover could take decades ( Stewart et al, 2016 ).…”

Niche partitioning and individual specialisation in resources and space use of sympatric fur seals at their range margin

“…Otariids, fur seals and sea lions, were ubiquitously overharvested for their fur from the eighteenth to twentieth century, with extinction of many populations and dramatic range reductions (Bonner 1989;Gerber & Hilborn 2001). With persistent conservation efforts, many species have been recovering in recent decades and reoccupying parts of their historic range (Wickens & York 1997;Gerber & Hilborn 2001;Kirkman et al 2013;Crespo 2021;Salton et al 2021). There are many incidences of two otariid species living in sympatry during such recoveries (Majluf & Trillmich 1981;Lyons et al 2000;Wege et al 2016;Elorriaga-Verplancken et al 2021), and while this seems to be possible by partitioning their niche (Robinson 2002;Franco-Trecu et al 2012;Páez-Rosas et al 2012;Jeglinski et al 2013;Pablo-Rodríguez et al 2016;Hoskins et al 2017) different levels of individual specialisations in diet and foraging among species may also play a role (Franco-Trecu 2014;Kernaléguen et al 2015a;Kernaléguen et al 2015b;Riverón et al 2021).…”

“…Here, we investigate how two otariids, the Australian fur seal, Arctocephalus pusillus doriferus, and the New Zealand fur seal, A. forsteri (also known as long-nosed fur seal, , coexist in sympatry at an expanding margin of both species' range. These species have recently reestablished seasonal occupation of their north-eastern range margin (Warneke 1975;Irvine et al 1997;Shaughnessy et al 2001;Burleigh et al 2008;Salton et al 2021) following broader population recovery and range expansion (Arnould et al 2003;McIntosh et al 2018).…”

“…The two species are typically considered 'generalists' due to their broad diets (Page et al 2005a;Kliska 2016), but in some areas Australian fur seals do exhibit individual specialisations in diet and foraging (Kernaléguen et al 2012;Kernaléguen et al 2016;Knox et al 2018). The two species have apparently distinct foraging modes, with Australian fur seals primarily foraging during benthic dives over the continental shelf (Knox et al 2017;Salton et al 2019) and New Zealand fur seals foraging during pelagic dives on and off the continental shelf (Page et al 2005b;Page et al 2006;Salton et al 2021). There is some evidence that the two species have different diets and foraging behaviour in this part of their range (Hardy et al 2017;Salton et al 2021), though the mechanisms for coexistence remains unclear.…”

“…The two species have apparently distinct foraging modes, with Australian fur seals primarily foraging during benthic dives over the continental shelf (Knox et al 2017;Salton et al 2019) and New Zealand fur seals foraging during pelagic dives on and off the continental shelf (Page et al 2005b;Page et al 2006;Salton et al 2021). There is some evidence that the two species have different diets and foraging behaviour in this part of their range (Hardy et al 2017;Salton et al 2021), though the mechanisms for coexistence remains unclear. Given the small population sizes of both species, we expect intraspecies competition to be low and, accordingly, interspecies interactions to drive niche partitioning.…”