DOI: 10.5061/dryad.k98sf7mgb
title: Does seasonal variation in the corticosterone response affect the nutritional ecology of a free-ranging lizard?

description: Challenging events in the environment that are both predictable (e.g.
 seasonal patterns in breeding activities) and unpredictable (e.g. predator
 encounter) are known to induce a glucocorticoid response that facilitates
 metabolic requirements during the challenge.   Given its role in
 mobilizing energy, glucocorticoid levels can influence the nutritional
 ecology of an individual by shifting dietary intake or retention patterns,
 but this relationship has not been tested in free-ranging vertebrates.
 Using a tropical lizard species (Psammophilus dorsalis) as a model system,
 we tested whether the elemental composition of dietary intake and
 excretion (faecal samples) varies with stress-induced corticosterone
 levels in males and females across different seasons. From free-ranging
 lizards in the wild, we measured levels of stress-induced corticosterone
 and glucose in blood and determined diet composition from gut-flushing.
 Elemental composition of the diet was determined by analysing the carbon
 and nitrogen content of identified prey Orders caught from the wild. We
 also collected faecal samples and estimated their elemental composition.
 We found that stress-induced corticosterone levels varied across seasons,
 with the lowest levels during the breeding season for both males and
 females. Despite high variation in corticosterone responsiveness, lizards
 did not shift the elemental composition of their diets and maintained an
 intake Carbon : Nitrogen ratio of 4.56. We did, however, find a negative
 correlation between stress-induced corticosterone levels and faecal
 elemental composition, suggesting selective retention of both carbon and
 nitrogen in individuals that have higher corticosterone responsiveness.
 This study highlights the interplay between corticosterone responsiveness
 and nutritional ecology, challenging the existing links in literature, and
 illustrating how free-ranging animals, such as lizards, adjust the
 elemental composition of excretion and not dietary intakes as a potential
 strategy to modulate natural physiological and ecological challenges.
description: We sampled adult <em>P. dorsalis</em> lizards of both
 sexes across three seasons (pre-breeding, early breeding, and late
 breeding) and multiple sites. We extracted 30-min handling stress-induced
 blood samples to quantify circulating glucose and corticosterone levels.
 Lizards were also gut flushed in the field to identifiy prey eaten in the
 wild to the level of Order. Identified prey Orders were later captured
 from the wild and subjected to a CHNS analysis to determine their carbon
 and nitrogen content. We used the absolute prey numbers identified in the
 diet, prey elemental content and prey mean weights to determine the total
 dietary elemental composition in terms of Carbon and Nitrogen. We also
 collected fecal samples from a separate group of lizards to determine the
 elemental composition (C and N) of feces. Additionally, we used pit-fall
 traps and sticky traps at the various sampling sites to determine the
 natural prey abundance.
description: # Does seasonal variation in the corticosterone response affect the
 nutritional ecology of a free-ranging lizard? ### Description of the data
 and file structure (Sheet 1) The data file contains data on lizard
 morphometrics, corticosterone hormone, circulating glucose, dietary C/N
 estimates and fecal C/N estimates for all lizards sampled across seasons
 and sites. The first column consists of the lizard ID (or unique
 identifier). Column 2 indicate the sex of the lizard ('f' for
 females and 'm' for males). Column 3 indicates the seasons
 lizards were sampled in (PB - Pre-breeding, EB - Early breeding, and B -
 Late breeding) Column 4 indicates the sites lizards were sampled from.
 Column 5 indicates the time points at which lizards were captured in the
 field Column 6 indicates the snout-vent length of lizards Column 7 and 8
 indicates the circulating glucose and 30-min stress-induced corticosterone
 levels respectively Column 9 indicates if diet sample (gut-flushed sample)
 was obtained for the lizard Columns 10 and 11 indicates the elemental
 composition of diet, such as Nitrogen (Ngm) and Carbon (Cgm) by weight (in
 gram) Columns 12 and 13 indicates the elemental composition of diet, such
 as Nitrogen (Diet_Npercent ) and Carbon (Diet_Cpercent) by percent (%)
 Column 14 indicates the dietary C:N ratio Column 15 indicates if fecal
 sample was obtained for the lizard Columns 16 and 17 indicates the
 elemental composition of feces, such as Nitrogen (Ngm_weight) and Carbon
 (Cgm_weight) by weight (in gram) Columns 18 and 19 indicates the elemental
 composition of feces, such as Nitrogen (Fecal_Npercent ) and Carbon
 (Fecal_Cpercent) by percent (%) Column 20 indicates the fecal C:N ratio
 ### Description of the data and file structure (Sheet 2) The data file
 contains data on prey absolute numbers identified from the gut-flush
 samples of lizards of both sexes across all there seasons and sites. The
 first column consists of the lizard ID (or unique identifier). Column 2
 indicate the sex of the lizard ('f' for females and
 'm' for males). Column 3 indicates the seasons lizards were
 sampled in (PB - Pre-breeding, EB - Early breeding, and B - Late breeding)
 Column 4 indicates the sites lizards were sampled from. Columns 5 to 13
 indicates the number of various insect Orders (count) identified in the
 diet of lizards, as indicated on the first row. ### Description of the
 data and file structure (Sheet 3) The data file contains data on prey
 absolute numbers identified from pit-fall traps and sticky traps across
 all sites in the Early breeding season used for determining natural prey
 abundance. The first column consists of the trap ID (or unique
 identifier). Column 2 indicates the sampling sites. Columns 3 to 11
 indicates the number of various insect Orders (count) identified from the
 traps, as indicated on the first row.