Abstract
Many broadly distributed migratory species exhibit fidelity to fine-scale areas that support vital life history requirements (e.g., resource acquisition, reproduction). Thus, such areas are critical for population dynamics and are of high conservation priority. Leatherback sea turtles are among the world’s most widely distributed species, and their breeding and feeding areas are typically separated by thousands of kilometres. In this study, we analysed turtle-borne video data on daytime feeding rates and energy acquisition in Nova Scotia, Canada, to quantify the importance of this discrete, seasonal foraging area for leatherback energy requirements. Based on daytime foraging only, we estimate that a single foraging season in Nova Scotia could support 59% of a non-breeding leatherback’s annual energy budget, and 29% of energetic requirements for a female on a typical 2-year reproductive cycle. However, maximum energy intake rates for leatherbacks are nearly four times lower than those of mammals and birds due the low energy content of leatherbacks’ gelatinous zooplankton prey. These results illustrate that high quality, local-scale foraging areas such as Nova Scotia are critically important to the stability and future growth of the leatherback population in the Northwest Atlantic Ocean. Thus, as with other migratory species, efforts to reduce threats and maintain habitat quality in such areas should be high conservation priorities.
Highlights
Migratory species present unique challenges to management due to their broad distributions; utilization of multiple, distinct habitat types during their life cycles; and exposure to diverse threats of varying magnitude across time and space[1,2,3,4,5]
Migratory marine species often exhibit remarkably fine-scale preferences for and fidelity to particular areas within their broad geographic distributions. These species have evolved suites of physiological and biological traits that allow them to detect and exploit areas that are critical to acquisition of resources in fulfilment of their life history requirements, namely reproduction[1,3,5]. Because these critical habitats have a disproportionate influence on population dynamics relative to their small spatial scales, identification of such areas provides conservation targets that are more logistically feasible to address, but that might result in higher return on investments to reduce threats and to protect or enhance available habitats[3,15]
Our analyses clearly demonstrate that this behaviour is energetically worthwhile: turtles can consume more than 200 kg, or more than 220 jellyfish per day (Table 2)—nearly 50% of their body mass daily—and these prey intake rates could fuel between 51% and 59% of leatherbacks’ total annual energy needs, and as much as 29% of a typical 2-yr reproductive cycle (Fig. 3)
Summary
Migratory species present unique challenges to management due to their broad distributions; utilization of multiple, distinct habitat types during their life cycles; and exposure to diverse threats of varying magnitude across time and space[1,2,3,4,5]. Efforts to assess conservation status and threats often focus on their broad-scale, international distributions, and on identification of overlaps with anthropogenic impacts, especially fishing activity[6,7,8,9,10] This approach attempts to match species’ distributions and habitat use to management-relevant scales, and it describes areas important for conservation based on patterns of high use inferred from remote sensing[11], high risk due to presence of threats and corresponding evidence of turtle-threat interaction[10], or a combination of both[12,13].
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