Finishing Up Peacocks
I read more in the research paper about peacock mate choice. The basic question of whether the long train of males was an honest indicator of mate health was answered in the affirmative on at least one measure: males with longer trains also were shown to have higher major histocompatibility complex (MHC) diversity. MHC diversity is linked to stronger immune function and parasite resistance. So females choosing a mate on the basis of the male in question having a long train brings along with it an indirect selection on increased MHC diversity. The further finding of the research was that females laid more eggs and larger eggs for males with higher MHC diversity, but that this was not a function of train length. The cueing signal for this effect was not discussed in the paper, but obviously has to be something other than train length. There are a large number of potential cues that might be obtained during mating, so at the moment it is just speculation as to which cue actually leads to the observed difference in female investment in offspring. Selection on train length brings the female and male together, but something else is signalling to the female how much to invest in that clutch of eggs. This is likely not under voluntary control, but rather a biochemical reaction (or reactions) leading to difference in egg size and number.
Developmental Windows
Something that you should know about behavior is that it develops or depends on cognitive functions that develop within an organism’s lifetime.
Sometimes learning about things like this can lead to sadness, if we have empathy with research subjects.
Cats and Stripes
Consider reacting to visual cues, like vertical or horizontal edges. Work done with cats (kittens, actually) shows that there is a limited period of time when the visual system can learn to recognize these sorts of stimuli. A kitten raised in an environment that only has one or the other of these cues grows up without the ability to recognize the other. It will walk directly into a wall painted in stripes of the other orientation. This disability does not go away with exposure to the other orientation of stripes — once past the developmental window, the cognitive ability to learn the “new” stripe orientation simply does not manifest. Acquiring a disability can be as simple as having the bad fortune to miss one of these developmental windows.
BrainFacts articles on critical periods
Work on such animal models isn’t necessarily heartless or without benefit to humans and the subject species. The stark reality that cognitive capability often follows from experience in a limited period of time in development has helped spur awareness in human parents of delays in human child development, and the need to seek help when such delays are noticed. One resource of interest promoting responsible use of animal models in research is the Foundation for Biomedical Research. (One of their most well-known media efforts was this poster.)
Development, Neoteny, and Tameness
Captive breeding on silver foxes shows that there is a whole behavioral suite that changes with selection for tameness.
Mavrik, the object of Trut’s attention, is about the size of a Shetland sheepdog, with chestnut orange fur and a white bib down his front. He plays his designated role in turn: wagging his tail, rolling on his back, panting eagerly in anticipation of attention. In adjacent cages lining either side of the narrow, open-sided shed, dozens of canids do the same, yelping and clamoring in an explosion of fur and unbridled excitement. “As you can see,” Trut says above the din, “all of them want human contact.” Today, however, Mavrik is the lucky recipient. Trut reaches in and scoops him up, then hands him over to me. Cradled in my arms, gently jawing my hand in his mouth, he’s as docile as any lapdog.
Except that Mavrik, as it happens, is not a dog at all. He’s a fox. Hidden away on this overgrown property, flanked by birch forests and barred by a rusty metal gate, he and several hundred of his relatives are the only population of domesticated silver foxes in the world. (Most of them are, indeed, silver or dark gray; Mavrik is rare in his chestnut fur.) And by “domesticated” I don’t mean captured and tamed, or raised by humans and conditioned by food to tolerate the occasional petting. I mean bred for domestication, as tame as your tabby cat or your Labrador. In fact, says Anna Kukekova, a Cornell researcher who studies the foxes, “they remind me a lot of golden retrievers, who are basically not aware that there are good people, bad people, people that they have met before, and those they haven’t.” These foxes treat any human as a potential companion, a behavior that is the product of arguably the most extraordinary breeding experiment ever conducted.
SciAm article on fox breeding experiment
NatGeo article on domestication
Peregrine Falcon Hunting
An example in the Halliday text is that of peregrine falcon hunting, and the observation that the observed effectiveness of this hunting in some individuals is indicative of a long history of practice and learning. We have already discussed how Harris’s hawk group members take up roles in cooperative hunting, but peregrines are solitary hunters. The inset on p. 36 indicates parental instruction occurs in peregrines:
Young peregrines spend two months in training after they fledge and before they leave their parents’ territory, while the parents attempt to impart some of this performance by coaching and example. Adults lead young in mock chases, and drop prey from above for the young to catch; if it is missed, the other parent flying below may catch it and, swooping up and over the student, reposition it to drop again. The young practice on insects and other easy prey, and indulge in dog fights among themselves. Even with this training, the first few months alone are extremely difficult for a young peregrine, and the period for highest mortality lies between leaving the nest and the first birthday.
Obtaining high speed in the stoop is a learned behavior. A falconer
Dolphin-Human Cooperative Fisheries
Reports of cooperation between dolphins and fisherman go back to antiquity, but in some locations in South America and Africa, such cooperative fisheries go on in the present. See pp. 47-48 of the Halliday text, which also describes a human-orca cooperative whale-hunting operation in Australia.
One of the South American cooperative fisheries has been observed by scientists (PDF), who conclude that this is a learned behavior passed down in maternal lines.
Trending News
Not actually animal behavior, but still interesting… the lab rat of botany, Arabidopsis thaliana, is reported to react to the vibrations of herbivores feeding on it with increased production of chemical defenses.
Plant germination and growth can be influenced by sound, but the ecological significance of these responses is unclear. We asked whether acoustic energy generated by the feeding of insect herbivores was detected by plants. We report that the vibrations caused by insect feeding can elicit chemical defenses. Arabidopsis thaliana (L.) rosettes pre-treated with the vibrations caused by caterpillar feeding had higher levels of glucosinolate and anthocyanin defenses when subsequently fed upon by Pieris rapae (L.) caterpillars than did untreated plants. The plants also discriminated between the vibrations caused by chewing and those caused by wind or insect song. Plants thus respond to herbivore-generated vibrations in a selective and ecologically meaningful way. A vibration signaling pathway would complement the known signaling pathways that rely on volatile, electrical, or phloem-borne signals. We suggest that vibration may represent a new long distance signaling mechanism in plant–insect interactions that contributes to systemic induction of chemical defenses.
Sensitivity and appropriate reaction to stimuli are not limited to the animal kingdom. One thing to note is that defense is expensive, and here we have research indicating that a plant species can engage in defense as needed, rather than commit resources to defense when not necessary.
A Personal Note
The morning of June 28th, I checked the mews for my 23-year-old Harris’s hawk, Rusty. She wasn’t in it. There had been storms the day previous. This instigated several days worth of activity and anxiety as Diane and I worked to try to relocate Rusty. Given that she was not wearing telemetry at the time, it was down to actually getting ourselves close to her, when we had no good notion of where she had gotten to. We managed that on the Tuesday morning following her disappearance, and we are happy to have her safely back home.
But that isn’t the way things often turn out. I have a blog post on the topic, Wildlife and Sad Endings, that you might be interested in.
Media Issues
During class discussion, it was brought up that PBS Nova received major funding from one of the billionaire Koch brothers, and that this likely meant that Nova would not cover issues that would discomfit such a benefactor. I had a look at the PBS Nova website for some of the issues they have taken up.
Inside the Megastorm (What made Hurricane Sandy so large.)
Hurricane Sandy and climate change
Megastorm Aftermath (How cities can prepare for major storms and rising seas.)
Secrets Beneath the Ice (Antarctica and potential damage from melting even part of its ice cover.)
Extreme Ice (“This NOVA-National Geographic Television special investigates the latest evidence of a radically warming planet.”)
Judgment Day: Intelligent Design on Trial
I think it was perhaps a bit too cynical a stance to assume that the Nova producers were so beholden to Koch money that they would not broach such topics.