Only child syndrome in snakes: Eggs incubated alone produce asocial individuals

Abstract

Egg-clustering and communal nesting behaviours provide advantages to offspring. Advantages range from anti-predatory benefits, maintenance of moisture and temperature levels within the nest, preventing the eggs from rolling, to enabling hatching synchrony through embryo communication. It was recently suggested that embryo communication may extend beyond development fine-tuning, and potentially convey information about the quality of the natal environment as well as provide an indication of forthcoming competition amongst siblings, conspecifics or even heterospecifics. Here we show that preventing embryos from communicating not only altered development rates but also strongly influenced post-natal social behaviour in snakes. Clutches of water snakes, Natrix maura, were split evenly into half-clutches and incubated as (1) clusters (i.e. eggs in physical contact with each other) or (2) as single eggs placed in individual goblets (i.e. no physical contact amongst sibling eggs). Single incubated eggs produced less-sociable young snakes than their siblings that were incubated in a cluster: the former were more active, less aggregated and physically contacted each other less often than the latter. Potential long-term effects and evolutionary drivers for this new example of informed dispersal are discussed.

High‐elevation hypoxia impacts perinatal physiology and performance in a potential montane colonizer

“…Because egg mass influences both embryo metabolism and hatching phenotype (Nelson et al 2004;Aubret 2013), and egg mass varied among clutches (Kruskal-Wallis test: H = 61.97, df = 10, P < 0.001), eggs were ranked within each clutch from lightest to heaviest and alternately assigned to treatments in order to ensure no difference in egg mass between treatments (Kruskal-Wallis test: H = 0.082, df = 1, P = 0.774). LE and EHE treatment half clutches were placed in a plastic container (20 cm × 15 cm × 5 cm) on a 2 cm layer of wet vermiculite (1:5 water to vermiculite by volume) and incubated in two identical incubation chambers (Ex-oTerra Model PT-2445, Rolf C. Hagen Inc., USA) set at a constant 28°C, a temperature successfully used for artificially incubating eggs of the viperine snake (Aubret 2013;Aubret et al 2016aAubret et al , 2017. Water bowls placed within each incubator ensured ambient humidity remained at 100% throughout incubation.…”

“…While further investigations are needed to address this question, there is evidence that incubation times (at 28°C) are heavily constrained in the viperine snake (i.e. always remain within a 24 h boundary, irrespective of experimental treatments; Aubret et al 2016aAubret et al ,b, 2017 and early hatching may entail deleterious effects. For example, early hatched Japanese quail chicks (Coturnix coturnix japonica) take 1-2 h longer to stand than normal chicks (Vince & Chinn 1971), while early hatched turtles (Chrysemys picta) showed reduced neuromuscular function for at least 9 months after hatching (Colbert et al 2010).…”

Yolk removal generates hatching asynchrony in snake eggs

“…Experimental evidence 10, 12, 18, 25, 26 suggests that synchronous hatching may be generated via (i) the alteration of development rates (i.e. metabolic compensation where less advanced eggs may accelerate development or smaller eggs may slow down development), or (ii) premature hatching (underdeveloped embryos hatch concurrently with full-term embryos, with potential detrimental effects).…”

“…Embryo communication in reptiles was shown to promote hatching synchrony primarily via metabolic compensation between more and less advanced eggs (in turtles 12 , 18 , 25 ; and snakes 26 ) or between large and smaller eggs (in snakes 10 ). Experimental evidence 10 , 12 , 18 , 25 , 26 suggests that synchronous hatching may be generated via (i) the alteration of development rates (i.e. metabolic compensation where less advanced eggs may accelerate development or smaller eggs may slow down development), or (ii) premature hatching (underdeveloped embryos hatch concurrently with full-term embryos, with potential detrimental effects).…”

Cold-blooded cognition: new directions in reptile cognition

“…Embryonic communication is well known in birds [30] although its effects on subsequent social behaviour is unknown. In reptiles, embryonic communication has recently been reported [31][32][33] and has been shown to influence behaviour post-hatching [34]. Hatchling water snakes (Natrix maura) from eggs incubated in isolation occupied a larger space, were more mobile and maintained less physical contact with conspecifics than counterparts incubated in a clutch where eggs were in contact [34].…”