Penguin Parents Won’t Chip In to Help Handicapped Spouse
* By Hadley Leggett Email Author
* July 2, 2009 |
Tired of your partner not helping out with the kids after you’ve had a tough day at work? At least you’re not a handicapped penguin parent trying to fish with a Plexiglas box strapped to your back.
Penguin pairs are known for their elaborate collaboration in raising chicks under harsh Antarctic conditions. But it turns out penguins will take teamwork only so far. When French scientists handicapped one bird from each of 46 pairs of Adélie penguins, partners of the unlucky birds didn’t step up to help out their mates, or to provide extra food for their chicks.
“In Adélie penguins, when one mate was handicapped, no compensatory care was observed from the partner,” researchers from the Institut Pluridisciplinaire Hubert Curien reported Tuesday in Animal Behaviour. “As a consequence, handicapped individuals and offspring both supported the whole additional breeding cost of the handicap.”
box1After a female penguin lays one or two eggs, she leaves the nest to forage for food while dad guards the eggs. Once the chicks hatch, mom and dad share equal responsibility for baby-rearing, with one parent enduring long periods of fasting to care for chicks while the other parent hunts at sea.
To study the effects of a handicap on pair cooperation, the researchers chose one unlucky bird from each penguin pair and attached a small Plexiglas box to its middle-back feathers. Similar to the first-generation tracking devices used by penguin researchers in the 1990s, the boxes were designed to increase underwater drag during diving and fishing, but not to interfere with the penguins’ other activities.
“According to previous studies, we could guess what the potential effects of the dummy devices would be on handicapped penguins, but not on their partner or their chicks,” animal ecologist Michael Beaulieu, a co-author on the study, wrote in an e-mail.
As expected, the handicapped penguins spent more time hunting at sea and came back with less food for their chicks. But instead of helping out, partners of the handicapped birds essentially ignored the plight of their unlucky mates. Partner penguins didn’t compensate by spending more time foraging for food or bringing back extra fish. And at the end of the study, while both handicapped birds and their chicks weighed less than their unhindered counterparts, the handicap-free partners stayed fat and happy.
It’s tempting to blame penguin partners for their negligence and insensitivity, especially because similar handicap studies in other species have shown that some birds, including passerines and great tits, do compensate for their mate’s deficiencies.
But Beaulieu has a different explanation: Because penguins are long-lived birds, it doesn’t make evolutionary sense for them to invest too much effort in any single reproductive season.
“Short-lived birds have only a few breeding attempts during their lifetime while long-lived birds have a lot,” he said. “As a result, short-lived birds are expected to give the maximum during one breeding season to increase the probability of survival of their current chicks.” Long-lived birds, on the other hand, should prioritize their own long-term survival over the outcome of individual chicks.
“Consequently, when the investment of the partner decreases,” Beaulieu said, “short-lived birds are expected to compensate while long-lived birds are expected to keep a fixed level of parental investment.”
The evolutionary explanation makes sense, but there’s one other possible explanation: It appears that male penguins don’t have great communication skills. Handicapped dads didn’t convey their distress to females after returning from a hunt, and when mom came back squawking about her feeding troubles, dad didn’t listen.
“If you do not ask for help, I will not help you,” Beaulieu said. “That may also explain why they did not compensate.”