Analysis of snakes’ sexual activity in the four months out of hibernation has confirmed that males' physiologically expensive approach to reproduction causes them to die earlier and in worse condition than females.
The relationship between body condition and age differed strikingly between sexes.
An international team of scientists led by the University of Sydney has confirmed a frenzied approach to the mating season is resulting in males dying earlier and in worse condition than their female counterparts, who prioritise body-maintenance over short-term reproductive success.
The study of red-sided garter snakes in North America found:
The research is published today in the Royal Society journal Proceedings B.
The study measured telomere length, which is a biomarker of ageing, in male and female snakes. The team found that males are unable to maintain good body condition and age faster than females. This is probably because males spend their energy on mating, instead of protecting against DNA and cellular damage associated with ageing. In contrast, females prioritise body condition and may be better able to repair cellular damage, leading to longer lives and future opportunities to reproduce.
Senior author from the University of Sydney, Dr Christopher R Friesen, explained that the males made good use of the relatively short amount of time to procreate, having only four months a year to breed, feed and have babies.
“Although we believe that all females mate every year, they only stay at the den sites (where mating takes place) for a short period of one- to three days; much less than males, who remain at least a week and up to 21 days,” Dr Friesen said.
“Females reproduce every other year, which depends on their stored fat/energy reserves. Our previous research has shown that females can store sperm for up to 15 months or more before she uses the sperm to fertilise her eggs!”
The paper reported: “The relationship between body condition and age differed strikingly between sexes, with females maintaining their body condition with age, while condition decreased with age in males.”
In addition to prioritising self-preservation over sex, the female garter snakes studied in Manitoba, Canada, did not waste energy on looking after their babies postnatally, which is in line with the parenting approach of other snakes.
The University of Sydney co-authors Dr Friesen and Nicky Rollings from the School of Life and Environmental Sciences and Dr Camilla Whittington (Sydney School of Veterinary Science) collaborated with co-authors Professor Mats Olsson, Goteborgs Universitet; Professor Robert Mason, Oregon State University; Associate Professor Heather Waye, University of Minnesota at Morris; Associate Professor Randolf Krohmer, Saint Xavier University and Dr Emily Uhrig, Linköping University.