A novel spatio-temporal scale based on ocean currents unravels environmental drivers of reproductive timing in a marine predator

Abstract

Life-history strategies have evolved in response to predictable patterns of environmental features. In practice, linking life-history strategies and changes in environmental conditions requires comparable space–time scales between both processes, a difficult match in most marine system studies. We propose a novel spatio-temporal and dynamic scale to explore marine productivity patterns probably driving reproductive timing in the inshore little penguin ( Eudyptula minor ), based on monthly data on ocean circulation in the Southern Ocean, Australia. In contrast to what occurred when considering any other fixed scales, little penguin's highly variable laying date always occurred within the annual peak of ocean productivity that emerged from our newly defined dynamic scale. Additionally, local sea surface temperature seems to have triggered the onset of reproduction, acting as an environmental cue informing on marine productivity patterns at our dynamic scale. Chlorophyll- a patterns extracted from this scale revealed that environment factors in marine ecosystems affecting breeding decisions are related to a much wider region than foraging areas that are commonly used in current studies investigating the link between animals' life history and their environment. We suggest that marine productivity patterns may be more predictable than previously thought when environmental and biological data are examined at appropriate scales.

Stable Isotopes (δ13C, δ15N) Combined with Conventional Dietary Approaches Reveal Plasticity in Central-Place Foraging Behavior of Little Penguins Eudyptula minor

“…In contrast, it may be possible that penguins were able to match time of breeding to marine productivity patterns (Afán et al, 2015). As expected for a generalist/opportunistic predator, observed changes in diet composition with a progressing season could be "simply" a passive reflection of changes in the availability of the main prey types.…”

“…Fluctuations in anchovy stocks have been attributed to changes in water temperature (Hoedt et al, 1996). So it is possible that similar ecological mechanisms are forcing the breeding dynamics of the little penguin colony at Phillip Island (Afán et al, 2015). Indeed, the unexplained deviance of our models could well be due to influence of environment factors, which was beyond of the purpose of this paper.…”

“…Age and individual quality can influence the onset of reproduction (Chiaradia and Nisbet, 2006;Nisbet and Dann, 2009). But at population level, little penguins respond to inter-annual variations in relevant oceanographic features and marine productivity patterns, probably driving patterns in the availability and distribution of prey (Afán et al, 2015). Very little information is available on the phenology of barracouta.…”

“…As expected for a generalist/opportunistic predator, observed changes in diet composition with a progressing season could be "simply" a passive reflection of changes in the availability of the main prey types. Indeed, reproduction takes place at the most favorable time of the year, and the onset of breeding is often dependent upon food availability (Meijer and Drent, 1999;Afán et al, 2015). Among the different breeding stages, chick rearing is a crucial phase for seabirds, in terms of reproductive requirements, as parents have to frequently return to their nest to provide their offspring with an adequate supply of food in order to be successful (Takahashi et al, 2003).…”

Key Questions in Marine Megafauna Movement Ecology

“…suitable water temperature, resting and breeding substrate) [44][45][46][47]. Migration patterns of marine megafauna will likely change to be more poleward with warming [48], although the complex effects of biotic interactions and habitat availability, for example, can lead to counter-intuitive re-distribution patterns in some taxa [49].…”