Data from: Desert lizards modulate their nutritional responses to match seasonal biological needs

Animals in extreme environments, such as deserts, experience severe
seasonal fluctuations in abiotic conditions and resources. Under these
conditions, they must obtain macronutrients in optimal amounts and ratios
to meet their nutritional requirements, which themselves vary with
seasonal changes in physiological and life-history processes. To
understand whether nutritional intakes and retention align with key
life-history events across seasons, we examined the nutritional ecology of
the desert-dwelling lizard Saara hardwickii. We first measured seasonal
variation in the quantity and quality of plants available for these
herbivorous lizards. By combining field observations of foraging behaviour
with elemental analysis, we determined carbon (C) and nitrogen (N) levels
in dietary intakes and faecal matter across seasons. Intake C: N was
lowest and faecal C: N highest in June, reflecting greater proportional
consumption and retention of N, likely meeting increased protein demands
during breeding. Conversely, dietary C: N and faecal %N were highest in
October, indicating greater consumption and retention of C prior to
hibernation. Surprisingly, these putative herbivores consumed insects only
around the breeding season, despite their year-round availability.
Overall, we show that S. hardwickii employs both behavioural diet choice
and post-ingestive physiology to match seasonal nutritional needs by
differentially consuming and retaining nutrients in an extreme
environment.