Survival Instincts Before Birth?!

Unborn delicate skinks hatch early to escape predation
(Source: OZWildlife)

Every animal is differently endowed with natural instincts to protect themselves from predators, but have you heard of instinct endowment even before birth? Hatching early from their eggs when startled by potential predators, the delicate skink (Lampropholis delicata) is endowed with such an ability to survive.

An interesting experiment conducted by Monash University’s School of Biological Sciences have shown that the premature hatching of the delicate skink is environmentally cued – by ‘knocking’ or ‘vibration’, an external disturbance that signals direct threat to the unborn reptile. In a first experiment that quantifies early hatching in lizards in response to mechanical stimulation, Sean Doody and Phillip Paull show that:

(1)     The influence of a predator increases the propensity of embryos to hatch;

(2)     Hatching in delicate skinks are explosive; delicate skinks possess an ability to accelerate and cover a significant ‘hatching sprint distance’ from the nest to escape its predator quickly; and that

(3)     There are associated potential costs that these skinks incur when they forego yolk absorption in order to hatch early.

Prior to this experiment, early hatching in response to predation was known from only amphibians, fish and invertebrates. This experiment thus confirms that un-hatched delicate skinks, equipped with the ability to react to motion disturbances outside its shell, exhibit this trait too.

Further, this experiment also seems to suggest that delicate skinks could well be ‘alive’ 3 to 4 days before its spontaneous hatching – a time-frame in which they are able to respond to external threat while feeding on the nutrients from the embryo. And although early hatchlings have smaller birth sizes, it definitely is a better choice than being preyed on!

With the ability to survive even before its birth – the delicate skink sure is cool!

Click on the video to see how an un-hatched lizard (in this case, a tegu) reacts to tickling!

REFERENCES

J. Sean Doody and Phillip Paull (2013). Hitting the Ground Running: Environmentally Cued Hatching in a Lizard. Copeia, March 2013, Vol. 2013, No. 1, pp. 160-165. Available at http://www.asihcopeiaonline.org.libproxy1.nus.edu.sg/doi/pdf/10.1643/CE-12-111. Accessed 06 April 2013.

Karen M. Warkentin (1995). Adaptive Plasticity in Hatching Age: A Response to Predation Risk Trade-offs. Ecology, April 1995, Vol. 92, pp. 3507 – 3510. Available at http://www.pnas.org/content/92/8/3507.full.pdf. Accessed 06 April 2013.

Karen M. Warkentin (2005). How do embryos assess risk? Vibrational Cues in Predator-Induced Hatching of Red-eyed Freetrogs. Animal Behaviour, May 2005, Vol. 70, pp. 59 – 71. Available at http://www.adamcstein.com/c1h3.pdf. Accessed 06 April 2013.