Measuring repeatability of compositional diet estimates: An example using quantitative fatty acid signature analysis.

By measuring the temporal consistency, or repeatability, in the diets of predators, we can gain a better understanding of the degree of individual specialization in resource utilization and implications for predator-prey interactions, population dynamics, and food web structure. To measure repeatability, we require repeated diet estimates of individuals over time, such as those derived from quantitative fatty acid signature analysis (QFASA), a popular diet estimation technique. However, diet estimates are often lengthy compositional vectors with many zeros, as some prey will not be consumed by all individuals, precluding the use of previously proposed measures of repeatability.

Validation of quantitative fatty acid signature analysis for estimating the diet composition of free-ranging killer whales.

Accurate diet estimates are necessary to assess trophic interactions and food web dynamics in ecosystems, particularly for apex predators like cetaceans, which can regulate entire food webs. Quantitative fatty acid analysis (QFASA) has been used to estimate the diets of marine predators in the last decade but has yet to be implemented on free-ranging cetaceans, from which typically only biopsy samples containing outer blubber are available, due to a lack of empirically determined calibration coefficients (CCs) that account for fatty acid (FA) metabolism. Here, we develop and validate QFASA for killer whales using full blubber from managed-care and free-ranging individuals.

Individual and population dietary specialization decline in fin whales during a period of ecosystem shift.

This study sought to estimate the effect of an anthropogenic and climate-driven change in prey availability on the degree of individual and population specialization of a large marine predator, the fin whale (Balaenoptera physalus). We examined skin biopsies from 99 fin whales sampled in the St. Lawrence Estuary (Canada) over a nine year period (1998-2006) during which environmental change was documented.

Exploring causal components of plasticity in grey seal birthdates: Effects of intrinsic traits, demography, and climate.

Change in breeding phenology is often a response to environmental forcing, but less is known of the mechanism underlying such changes and their fitness consequences. Here, we report on changes in the breeding phenology from a 27-year longitudinal study (1991-2017) of individually marked, known-aged grey seals () on Sable Island, Nova Scotia, Canada. We used generalized linear mixed models and a 3-step process to develop a model that includes interactions between intrinsic and extrinsic covariates and to test hypotheses about the influence of fixed factors (maternal age, parity, previous reproductive success, pup sex, colony density, Atlantic Multidecal Oscillation (AMO), North Atlantic Oscillation (NAO), and Sea Surface Temperature) and a random factor (female identity) on parturition dates.

Seasonal occupancy and connectivity amongst nearshore flats and reef habitats by permit Trachinotus falcatus: considerations for fisheries management.

We used acoustic telemetry to quantify permit Trachinotus falcatus habitat use and connectivity in proximity to the Florida Keys, USA, and assessed these patterns relative to current habitat and fisheries management practices. From March 2017 to June 2018, 45 permit tagged within 16 km of the lower Florida Keys were detected at stationary acoustic receivers throughout the south Florida region, the majority of which remained within the Special Permit Zone, where more extensive fisheries harvest regulations are implemented. There was a high level of connectivity between nearshore flats (i.

Egg size is independent of variation in pre-breeding feather corticosterone in Cassin's auklets during favorable oceanographic conditions.

The measurement of corticosterone levels in feathers (fCort) is gaining recognition as an effective means for describing links between stages of the annual cycle in birds. Many seabirds are especially good models for exploring these links, or carryover effects, due to their migratory behavior and reproductive investment in a single-egg clutch. Here, we measure fCort in Cassin's auklet (Ptychoramphus aleuticus) breast feathers at two colonies in British Columbia during 2011, a year of favorable oceanographic conditions, and examine its relationship with egg size.

A novel approach to quantifying the spatiotemporal behavior of instrumented grey seals used to sample the environment.

Background: Paired with satellite location telemetry, animal-borne instruments can collect spatiotemporal data describing the animal's movement and environment at a scale relevant to its behavior. Ecologists have developed methods for identifying the area(s) used by an animal (e.g.

ECOLOGY. Aquatic animal telemetry: A panoramic window into the underwater world.

The distribution and interactions of aquatic organisms across space and time structure our marine, freshwater, and estuarine ecosystems. Over the past decade, technological advances in telemetry have transformed our ability to observe aquatic animal behavior and movement. These advances are now providing unprecedented ecological insights by connecting animal movements with measures of their physiology and environment.

Offspring size at weaning affects survival to recruitment and reproductive performance of primiparous gray seals.

Offspring size affects survival and subsequent reproduction in many organisms. However, studies of offspring size in large mammals are often limited to effects on juveniles because of the difficulty of following individuals to maturity. We used data from a long-term study of individually marked gray seals (Halichoerus grypus; Fabricius, 1791) to test the hypothesis that larger offspring have higher survival to recruitment and are larger and more successful primiparous mothers than smaller offspring.

Local contamination, and not feeding preferences, explains elevated PCB concentrations in Labrador ringed seals (Pusa hispida).

Polychlorinated biphenyls (PCBs) in high trophic level species typically reflect the contributions of myriad sources, such that source apportionment is rarely possible. The release of PCBs by a military radar station into Saglek Bay, Labrador contaminated the local marine food web. For instance, while heavier (higher chlorinated) PCB profiles in some ringed seals (Pusa hispida) were previously attributed to this local source, differences in feeding preferences among seals could not be ruled out as a contributing factor.

Probability of detecting marine predator-prey and species interactions using novel hybrid acoustic transmitter-receiver tags.

Understanding the nature of inter-specific and conspecific interactions in the ocean is challenging because direct observation is usually impossible. The development of dual transmitter/receivers, Vemco Mobile Transceivers (VMT), and satellite-linked (e.g.

The sun, moon, wind, and biological imperative-shaping contrasting wintertime migration and foraging strategies of adult male and female northern fur seals (Callorhinus ursinus).

Adult male and female northern fur seals (Callorhinus ursinus) are sexually segregated in different regions of the North Pacific Ocean and Bering Sea during their winter migration. Explanations for this involve interplay between physiology, predator-prey dynamics, and ecosystem characteristics, however possible mechanisms lack empirical support. To investigate factors influencing the winter ecology of both sexes, we deployed five satellite-linked conductivity, temperature, and depth data loggers on adult males, and six satellite-linked depth data loggers and four satellite transmitters on adult females from St.

Validation of adipose lipid content as a body condition index for polar bears.

Body condition is a key indicator of individual and population health. Yet, there is little consensus as to the most appropriate condition index (CI), and most of the currently used CIs have not been thoroughly validated and are logistically challenging. Adipose samples from large datasets of capture biopsied, remote biopsied, and harvested polar bears were used to validate adipose lipid content as a CI via tests of accuracy, precision, sensitivity, biopsy depth, and storage conditions and comparisons to established CIs, to measures of health and to demographic and ecological parameters.

Characterization of blubber fatty acid signatures in northern elephant seals (Mirounga angustirostris) over the postweaning fast.

Phocids routinely fast for extended periods. During these fasts, energetic requirements are met primarily through the catabolism of blubber lipid. To assess whether fatty acid (FA) composition changes during the postweaning fast in northern elephant seals, blubber biopsies were acquired longitudinally from 43 pups at 2.

Global change effects on the long-term feeding ecology and contaminant exposures of East Greenland polar bears.

Rapid climate changes are occurring in the Arctic, with substantial repercussions for arctic ecosystems. It is challenging to assess ecosystem changes in remote polar environments, but one successful approach has entailed monitoring the diets of upper trophic level consumers. Quantitative fatty acid signature analysis (QFASA) and fatty acid carbon isotope (δ(13) C-FA) patterns were used to assess diets of East Greenland (EG) polar bears (Ursus maritimus) (n = 310) over the past three decades.

Animal-borne acoustic transceivers reveal patterns of at-sea associations in an upper-trophic level predator.

Satellite telemetry data have substantially increased our understanding of habitat use and foraging behaviour of upper-trophic marine predators, but fall short of providing an understanding of their social behaviour. We sought to determine whether novel acoustic and archival GPS data could be used to examine at-sea associations among grey seals (Halichoerus grypus) during the fall foraging period. Fifteen grey seals from Sable Island, Canada were deployed with Vemco Mobile Transceivers and Satellite-GPS transmitters in October 2009, 13 of which were recaptured and units retrieved 79 ± 2.

Primiparous and multiparous females differ in mammary gland alveolar development: implications for milk production.

Mammary gland capacity is influenced by the number of secretory cells in the gland, the activity of those cells and the size and arrangement of the alveoli that they form. Although reproductive experience has been shown to affect the total number of secretory cells in the gland, its potential effect on the structural development of lobulo-alveolar tissues has not been directly investigated. To examine whether reproductive experience affects lobulo-alveolar development, we took mammary gland biopsies at early and peak lactation from primiparous and multiparous grey seal (Halichoerus grypus) females and used histological techniques to compare cell density, alveolar density and alveolar size within secretory lobules.

Jellyfish support high energy intake of leatherback sea turtles (Dermochelys coriacea): video evidence from animal-borne cameras.

The endangered leatherback turtle is a large, highly migratory marine predator that inexplicably relies upon a diet of low-energy gelatinous zooplankton. The location of these prey may be predictable at large oceanographic scales, given that leatherback turtles perform long distance migrations (1000s of km) from nesting beaches to high latitude foraging grounds. However, little is known about the profitability of this migration and foraging strategy.

The influence of reproductive experience on milk energy output and lactation performance in the grey seal (Halichoerus grypus).

Although evidence from domestic and laboratory species suggests that reproductive experience plays a critical role in the development of aspects of lactation performance, whether reproductive experience may have a significant influence on milk energy transfer to neonates in wild populations has not been directly investigated. We compared maternal energy expenditures and pup growth and energy deposition over the course of lactation between primiparous and fully-grown, multiparous grey seal (Halichoerus grypus) females to test whether reproductive experience has a significant influence on lactation performance. Although there was no difference between primiparous females in milk composition and, thus, milk energy content at either early or peak lactation primiparous females had a significantly lower daily milk energy output than multiparous females indicating a reduced physiological capacity for milk secretion.

Validating quantitative fatty acid signature analysis to estimate diets of spectacled and Steller's eiders (Somateria fischeri and Polysticta stelleri).

Fatty acid (FA) signature analysis has been used to study foraging ecology and food webs in marine ecosystems. This powerful method provides information about diets over an extended time period (e.g.

The effects of diet and caloric restriction on adipose tissue fatty acid signatures of tufted puffin (Fratercula cirrhata) nestlings.

Fatty acid (FA) signature analysis is a powerful tool to investigate foraging ecology and food web dynamics in marine ecosystems. However, use of FA signatures to qualitatively or quantitatively infer diets is potentially complicated by effects of nutritional state on lipid metabolism. Estimation of diets using the quantitative fatty acid signature analysis (QFASA) model requires the use of calibration coefficients to account for predator metabolism of individual FAs.

Body condition at weaning affects the duration of the postweaning fast in gray seal pups (Halichoerus grypus).

Gray seals (Halichoerus grypus) undergo a terrestrial postweaning fast (PWF) that depletes energy reserves acquired during the suckling interval. Plasticity in PWF duration may ensure that pups of variable body condition depart for sea with adequate energy reserves. To test this hypothesis, we examined body condition of 30 gray seal pups at weaning and monitored their PWF duration.

Fatty acid signatures of stomach oil and adipose tissue of northern fulmars (Fulmarus glacialis) in Alaska: implications for diet analysis of Procellariiform birds.

Procellariiforms are unique among seabirds in storing dietary lipids in both adipose tissue and stomach oil. Thus, both lipid sources are potentially useful for trophic studies using fatty acid (FA) signatures. However, little is known about the relationship between FA signatures in stomach oil and adipose tissue of individuals or whether these signatures provide similar information about diet and physiology.

Sex differences in grey seal diet reflect seasonal variation in foraging behaviour and reproductive expenditure: evidence from quantitative fatty acid signature analysis.

1. Intraspecific variation in diet can be an important component of a species niche breadth. We tested the hypothesis that sex differences in seasonal foraging behaviour and energy storage of sexually size dimorphic grey seals Halichoerus grypus (Fabrisius 1971) are reflected in differences in the diet and niche breadth.