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Postnatal growth rate varies with latitude in range-expanding geese – the role of plasticity and day length

Citation

Boom, Michiel P. et al. (2021), Postnatal growth rate varies with latitude in range-expanding geese – the role of plasticity and day length, Dryad, Dataset, https://doi.org/10.5061/dryad.qjq2bvqhc

Abstract

This dataset contains data from an analysis of differences in growth rate among three different barnacle populations breeding at different latitudes, described in the paper:
Boom, Michiel P., van der Jeugd, H.P., Steffani, B., Nolet, B.A., Larsson, K., & Eichhorn, G. (2021), Postnatal growth rate varies with latitude in range-expanding geese – the role of plasticity and day length. Journal of Animal Ecology.

The postnatal growth period is a crucial life stage, with potential lifelong effects on an animal’s fitness. How fast animals grow depends on their life history strategy and rearing environment, and interspecific comparisons generally show higher growth rates at higher latitudes. However, to elucidate the mechanisms behind this gradient in growth rate, intraspecific comparisons are needed.

Recently, barnacle geese expanded their Arctic breeding range from the Russian Barents Sea coast southwards, and now also breed along the Baltic and North Sea coasts. Baltic breeders shortened their migration, while barnacle geese breeding along the North Sea stopped migrating entirely.

We collected cross-sectional data on gosling tarsus length, head length and body mass, and constructed population-specific growth curves to compare growth rates among three populations (Barents Sea, Baltic Sea and North Sea) spanning 17° in latitude.

Growth rate was faster at higher latitudes, and the gradient resembled the latitudinal gradient previously observed in an interspecific comparison of precocial species. Differences in day length among the three breeding regions could largely explain the observed differences in growth rate. In the Baltic, and especially in the Arctic population, growth rate was slower later in the season, most likely because of the stronger seasonal decline in food quality.

Our results suggest that differences in postnatal growth rate between the Arctic and temperate populations are mainly a plastic response to local environmental conditions. This plasticity can increase the individuals’ ability to cope with annual variation in local conditions, but can also increase the potential to re-distribute and adapt to new breeding environments. 

Methods

We collected biometric data on growing goslings during long-term studies in colonies from three study-populations: 1) A long-distance migratory population breeding in the Arctic in Kolokolkova Bay along the Barents Sea coast (68°35’N, 52°20’E), data collected in 6 years between 2003 and 2015; 2) A short-distance migratory population breeding on Gotland in the Baltic Sea (57°25’N, 18°53’E) data collected in 15 years between 1986 and 2000; 3) A sedentary population breeding in the Netherlands along the North Sea (51°40’N, 4°14’E) data collected in 5 years between 2004 and 2018 (Larsson et al., 1988; Van der Jeugd et al., 2003, 2009; Eichhorn et al., 2010).

Our analysis is based on all measured goslings with known age (Sample sizes: Barents Sea = 392; Baltic Sea = 933; North Sea = 116). Sex was determined based on cloacal inspection. Goslings were weighed in a bag using a Pesola spring scale with an accuracy of ± 5 g (if <600 g) or a digital hand scale or Pesola spring scale with an accuracy of ± 10 g (if >600 g). A calliper (± 0.1 mm) was used to measure the outer length of the bent tarsus. Head length was measured using a ruler (± 1 mm).

The number of daylight hours that had accumulated between hatching and capture was calculated for each gosling. Daylight was determined as the period between dawn and dusk, and was calculated based on the coordinates of the three breeding colonies using the R package “Suncalc” (see associated manuscript referenced above).

We calculated relative hatch dates by centralizing hatch dates within each cohort, because years can differ in onset of spring and consequently in timing of breeding and hatching. For the calculation of the relative hatch date for each gosling, we used the mean hatch date of the colonies (not only of the recaptured goslings), as established from nest monitoring (see associated manuscript referenced above for details).

Usage Notes

In the ReadMe file, a description of the variables in the dataset can be found, including the data type and measurement unit. The explanation column includes a clarification of the variable.

In general, all measurements were taken from each individual gosling. However, on rare occasions one measurement was overlooked, resulting in a few missing values (NA = value not available)