Does Promiscuity Prevent Extinction?

(Feb. 26, 2010) — Promiscuous females may be the key to a species' survival, according to new research by the Universities of Exeter and Liverpool. Published February 25 in Current Biology, the study could solve the mystery of why females of most species have multiple mates, despite this being more risky for the individual.

These are Drosophila pseudoobscura mating. A new study by the Universities of Exeter and Liverpool, UK, on these fruitfly suggests promiscuous females may be the key to a species' survival. (Credit: University of Exeter)

Known as 'polyandry' among scientists, the phenomenon of females having multiple mates is shared across most animal species, from insects to mammals. This study suggests that polyandry reduces the risk of populations becoming extinct because of all-female broods being born. This can sometimes occur as a result of a sex-ratio distortion (SR) chromosome, which results in all of the Y chromosome 'male' sperm being killed before fertilisation. The all-female offspring will carry the SR chromosome, which will be passed on to their sons in turn resulting in more all-female broods. Eventually there will be no males and the population will die out.

For this study, the scientists worked with the fruitfly Drosophila pseudoobscura. They gave some populations the opportunity to mate naturally, meaning that the females had multiple partners. The others were restricted to having one mate each. They bred several generations of these populations, so they could see how each fared over time.

Over fifteen generations, five of the twelve populations that had been monogamous became extinct as a result of males dying out. The SR chromosome was far less prevalent in the populations in which females had the opportunity to have multiple mates and none of these populations became extinct.

The study shows how having multiple mates can suppress the spread of the SR chromosome, making all-female broods a rarity. This is because males that carry the SR chromosome produce only half as many sperm as normal males. When a female mates with multiple males, their sperm will compete to fertilise her eggs. The few sperm produced by males carrying the SR chromosome are out-competed by the sperm from normal males, and the SR chromosome cannot spread.

Lead author Professor Nina Wedell of the University of Exeter said: "We were surprised by how quickly -- within nine generations -- a population could die out as a result of females only mating with one partner. Polyandry is such a widespread phenomenon in nature but it remains something of an enigma for scientists. This study is the first to suggest that it could actually save a population from extinction."

This study was funded by the Natural Environment Research Council.

Key Largo gets some wood rats back

Seven Key Largo wood rats -- from a kinder, gentler rodent strain than the one humans abhor -- were released into their only known home.

This is one of seven Key Largo wood rats taken to Crocodile Lake National Wildlife Refuge. LOWRY PARK ZOO/TAMPA

Photo By CURTIS MORGAN
The seven pioneers spent the week preparing for their upcoming ordeal in North Key Largo, sampling berries and other local fare, redecorating homes with sticks, leaves and whatever else they got their little paws on, and generally getting used to life outside a cage at Disney World.

On Tuesday, scientists lifted protective enclosures to release captive-bred Key Largo wood rats into Crocodile Lake National Wildlife Refuge -- the first test of a restocking experiment that might represent the last and best hope for an obscure rodent that ranks among Florida's rarest species.

So far, so good. Feral cats and Burmese pythons didn't immediately swallow any, and the lab rats -- products of a breeding program run by the U.S. Fish and Wildlife Service, Tampa's Lowry Park Zoo and Disney's Animal Kingdom -- showed some of the skills and instincts they'll need to survive.

For one, they've lived up to another name they sometimes go by: pack rat. They've busily added to nests -- distinctive mounds cobbled with everything from sticks to dung to the random bottle cap -- that were vacated by other members of their vanishing population.

``They've piled so much stuff over the nests it's incredible,'' said Sandra Sneckenberger, a Wildlife Service biologist.

The Service started the breeding program in 2002 as a last-resort attempt to reverse the population decline in the rat's only known home, the tangled hardwood hammocks of the largest island in the Florida Keys chain. The estimated population has dwindled to no more than 300 -- down dramatically from about 6,500 before 1984, when the rat was added to the federal endangered species list.

Though they are rats, they are a different genus than the nasty, biting carriers of disease reviled by humans, said Christy Alligood, a research specialist at Disney's Animal Kingdom. The wood rat arises from a kinder, gentler rodent strain and wants nothing to do with homes or buildings. In nature and size, they're more akin to mice -- small at just four to nine inches, docile and shy.

Though handling the seven was kept to a minimum to help acclimate them to the wild, biologists and breeding teams grew attached enough to name them, Sneckenberger said. ``They are very charismatic creatures.''

The first group of seven -- Tweak, Ralph, Roxy, Frieda, Rosie, Fern, and Garfunkle -- will be followed by seven others later this month. The rats, fitted with tiny radio collars, will be tracked for 60 days. If they survive, the hope is they'll breed.

It's not something they do all that frequently in the wild, which might partially account for the species' decline. Unlike prolific urban rats, wood rats breed only two to three times a year, producing about two ``pups'' each time, Alligood said. Otherwise, they tend to be solitary homebodies.

Getting them together in captivity proved one of the major challenges for the eight-year breeding program, she said. If they weren't in the mood, they might even attack each other. Researchers and technicians at the Animal Kingdom's Conservation Station learned to recognize the signs of a ``receptive'' wood rat, including a tell-tale, high-pitched raspy chirp.

Development, the most prevalent threat to wildlife in Florida, certainly played a role in reducing the rat's prime habitat, but its most recent rapid decline, starting around 1995, happened with much of its remaining habitat under state and federal protection.

The dire drop remains somewhat of a puzzle to scientists.

Tracking the lab rats also might help sort out threats, including diseases associated with a round-worm found in raccoon feces, as well as Key Largo's problematic population of feral cats and Burmese pythons.

Rat remains have been found in the guts ofat least two captured snakes.

Off-duty Collier deputy bit by water moccasin at kids fishing event

NAPLES — It could have been a lot worse.


That’s how Robert Brown described getting nicked by a water moccasin Saturday during the Collier County Sheriff’s Office “Kids Love Fishing” event at Florida Sports Park in East Naples.

“It was one of those things,” said Brown, an amateur herpetologist and a Sheriff’s Office sergeant who has worked with snakes for more than 35 years. “If someone had to get bit, it was better that it was me rather than a kid.”

Brown, who was off-duty during Saturday’s event, had been on hand to help the Collier County Junior Deputies League at its Camp Discovery at the Florida Sports Park when he saw a group of kids gathering around what they thought was a non-venomous corn snake.

“I grabbed him, made them safer, and explained that it was a water moccasin,” said Brown, 47. “They got to see what venomous snakes look like and learned not to touch them.”

But the learning experience got a little more real, when the 18-inch male decided he didn’t like being handled.

“He just twisted his head ever so slightly,” said Brown. “It was operator error. They are sneaky that way. He hooked me with a fang.”

Water moccasins, also commonly known as cottonmouths or pit vipers, are venomous snakes that can deliver a painful and potentially fatal hemotoxin in their bite, said Naples Zoo Executive Director David Tetzlaff.

“It basically affects your blood,” said Tetzlaff. “A bite from a pit viper can make you bleed to death internally.”

Realizing that, Brown said he headed south of the park to Physician’s Regional Hospital-Collier Boulevard for treatment after making sure the snake was back in its natural habitat and away from the children.

“They gave me a little anti-venom and let (the wound) drain out,” said Brown, who was still as the hospital as of Monday afternoon.

Brown admitted that he was very lucky, because he could have been bitten by a coral snake — one of Florida’s four venomous snakes — which injects a neurotoxin that causes paralysis and eventually can stop a person’s heart.

The pygmy rattlesnake and the eastern diamondback snake are the two other venomous snake species in Florida, and both deliver hemotoxin in their bites.

“It’s not always the size of the snake, it’s the amount of venom that gets you,” he said.

First introduced to venomous snakes as a Boy Scout in New York, Brown said his love for herpetology — the study of amphibians and reptiles — continued long after his family moved down to Florida.

“I’ve been dealing with venomous snakes for 35 years, and it’s the first time I was bit,” said Brown, adding that his father has been bitten by snakes twice.

As for why the water moccasin got a reprieve, Brown said, the snake was just in the wrong place at the wrong time.

“It was a beautiful snake, so we let him go in a non-populated area,” said Brown. “The snake didn’t do anything wrong.