Productive foraging grounds enhance maternal condition and offspring quality in a capital breeding species

Abstract

Feeding ecology is an essential component of an organism's life, but foraging comes with risks and energetic costs. Species in which populations exhibit more than one feeding strategy, such as sea turtles, are good systems for investigating how feeding ecology impacts life-history traits, reproduction and carried over effects across generations. Here, we investigated how the feeding ecology of loggerhead sea turtles (Caretta caretta) nesting at the Cabo Verde archipelago correlates with reproductive outputs and offspring quality. We determined the feeding ecology of female turtles before and during the breeding season from stable isotope analysis of carbon and nitrogen and correlated isotopic ratio with female and offspring traits. We found that female turtles feeding at higher trophic positions produced larger clutches. We also found that females with higher δ¹³C values, typical of productive foraging areas, had greater fat reserves, were less likely to be infected by leech parasites and produced heavier offspring. The offspring of infected mothers with higher δ¹³C values performed best in crawling and self-righting trials than those of non-infected mothers with higher δ¹³C values. This study shows adult female loggerheads that exploit productive areas build capital reserves that impact their reproductive success and multiple proxies for offspring quality. Overall, our findings provide valuable insights into the complex interplay between feeding ecology and reproductive success, and reveal the transgenerational carry-over effects of both feeding ecology and health on offspring quality in sea turtles.

Keywords: energetic resources; foraging; loggerhead sea turtle; nesting; offspring fitness; reproduction; stable isotope analysis.

FIGURE 1

Map of the Cabo Verde archipelago located off the west coast of Africa.

FIGURE 2

Change in stable isotope values over the 2018 nesting season. (a) Both skin (n = 242) δ¹⁵N (F _1,237 = 24.675, p < .001) and plasma (n = 215) δ¹⁵N (F _1,210 = 10.315, p = .002) increased over the season. (b) No trend in skin δ¹³C was seen over time (F _1,237 = 0.093, p = .76), whereas plasma δ¹³C increased (F _1,210 = 22.206, p < .001).

FIGURE 3

(a) Body fat reserves—the residuals of the relationship between body fat measurements against the CCL—(n = 227) and (b) curved carapace length (CCL; n = 242) of adult female loggerhead sea turtle during the 2018 nesting season on Sal Island, Cabo Verde. Body fat reserves of sea turtles significantly declined over the nesting season (F _1,162 = 32.471, p < .001) whereas CCL showed no significant change (F _1,237 = 2.818, p = .095), suggesting no cohort effects in the arrival to the nesting ground.

FIGURE 4

Relationship of turtle (n = 227) skin δ¹³C to body fat (fat reserves regressed against season period) in combination with (a) nesting season period (F _2,207 = 7.695, p < .001) and (b) turtle infection status (F _1,207 = 5.013, p = .026).

FIGURE 5

Clutch size (n = 226) positively correlated with δ15N values in the skin (F _1,199 = 6.010, p = .015).

FIGURE 6

Scatterplots that show hatchling self‐righting and crawl time result with skin δ¹³C and maternal parasites presence. We found that offspring of infected mothers were faster in (a) self‐righting (F _1,69 = 5.622, p = .021) and (b) crawl speed (F _1,69 = 7.814, p = .007) tests.