Abstract
Increases in ocean temperature are associated with changes in the distribution of fish stocks, and the foraging regimes and maternal attendance patterns of marine mammals. However, it is not well understood how these changes affect offspring health and survival. The maternal attendance patterns and immunity of South American fur seals were assessed in a rookery where hookworm disease is the main cause of pup mortality. Pups receiving higher levels of maternal attendance had a positive energy balance and a more reactive immune system. These pups were able to expel hookworms through a specific immune mediated mechanism and survived the infection. Maternal attendance was higher in years with low sea surface temperature, therefore, the mean hookworm burden and mortality increased with sea surface temperature over a 10-year period. We provide a mechanistic explanation regarding how changes in ocean temperature and maternal care affect infectious diseases dynamics in a marine mammal.
Highlights
Marine mammals are a diverse group of top predators highly sensitive to changes in aquatic ecosystems (Constable et al, 2014)
Between 81% to 100% of pups examined through necropsy between 2005–08 (n = 124) and 2012–17 (n = 154) had evidence of hookworm infection, and hookworm-related mortality corresponded to 13–50% of all pups found dead (n = 56, Figure 1B)
As otariid maternal care is influenced by ocean environmental conditions and prey availability (Trillmich et al, 1991; Soto et al, 2006; Jeanniard-du-Dot et al, 2017), indirect indicators of ocean productivity such as sea surface temperature are correlated with hookworm disease dynamics and overall fur seal pup survival
Summary
Marine mammals are a diverse group of top predators highly sensitive to changes in aquatic ecosystems (Constable et al, 2014). Within this group, fur seals and sea lions (otariids) breed and give birth on land but forage at sea, alternating periods of foraging in the ocean with periods of offspring attendance and nursing on land (income breeders) (Stephens et al, 2009). Otariids, like other marine mammals, are highly sensitive to local changes in prey distribution and abundance (Trillmich et al, 1991, Constable et al, 2014, Elorriaga-Verplancken et al, 2016).
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