Supporting information for: When to shed? Patterns and drivers of time to first ecdysis in snakes

Time from birth or hatching to the first shed (postnatal ecdysis) in
snakes ranges from about an hour to several weeks depending upon the
species. We assessed patterns in time to postnatal ecdysis in 102 snake
species for which we could source appropriate information, covering 2.6%
of all extant snake species, and related measures to various biological
traits. Reconstruction revealed ancestral time to postnatal ecdysis to be
eleven days. Since time to postnatal ecdysis can be shorter or longer than
the ancestral state, we argue that there are several competing drivers for
time to postnatal ecdysis. A reduced time to postnatal ecdysis has evolved
in several lineages, commonly in ambush-foraging, viviparous vipers, while
extended time to postnatal ecdysis is associated with oviparous species
with maternal care. Of central importance is the impact of postnatal
ecdysis on the scent levels of neonates, resulting in a reduction of time
to postnatal ecdysis in chemically cryptic species, while the pivotal role
of scent in mother-neonate recognition has resulted in the retention or
extension of time to postnatal ecdysis. We showed that postnatal ecdysis
improves chemical crypsis. The patterns revealed in this study suggest
that measures of time to postnatal ecdysis can provide insights into the
biology of snakes and be used as an indicator of certain life history
traits.