news bits
Camas pocket gophers are easy to see right now below the NE overlook in Ankeny NWR, Oregon. The best time is the last two hours before dawn. You need moonlight as they are extremely wary of spotlights.
A study in Chile found that melanistic cats are more nocturnal than spotted ones. I wonder how it works: is activity pattern genetically linked to color, or do cats somehow understand when they are least visible? Cool either way.
Also, HMW has finally realized that attempting to cover all rodents in one volume would be a disaster, and is conducting a poll on splitting the volume in two. Please vote for two: one would be a waste of money 🙂
Vladimir Dinets
8 Comments
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vdinets
It’s not that simple. Remember, we are not talking about different species here. Melanism is caused by a single-allele difference; black and spotted kittens are often found in the same litter. In order to be useful, inherited behavioral differences must be somehow genetically linked to color differences.
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Farnborough John
Yes but it doesn’t have to be inherited behavioural difference. They could behave exactly the same between black and spotted and the black would still end up commoner in the night hunting group because it is the behaviour of the prey that acts upon the individuals’ success and it will act on every generation exactly the same. The effect may even only be within and not between generations in a kind of “game reset” way.
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vdinets
You mean, black cats learn to be more nocturnal because that’s when hunting is better for them? That’s certainly possible. Also, it is a testable hypothesis: if it’s true, experienced cats of different color should differ in activity patterns more than subadults.
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Jurek
I think it is learned mechanism. Cats learn that their hunt at daytime is not successful but at night is, and so switch their strategy.
In moths, even simpler mechanism makes sure that it always roosts on a cryptic background. A moth cannot see itself or its roost in much detail. It lands anywhere, and is disturbed and flies again, until it lands on a place matching its colors.
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vdinets
Could be. But are you sure about moths? The last time I looked into it (about ten years ago), their ability to find matching backgrounds was a mystery.
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Farnborough John
From what I remember Jurek is more or less right. Peppered Moth is the archetype of this as it has two very distinctive colour morphs, very dark and very light. In Victorian Britain the dark morph predominated in sooty cities while the light morph survived better in the more varied background of the countryside. Both land anywhere but against the uniform dark background of the cities the light morph were predated out of existence and the local gene pool.
I believe the situation is now much more even as the environment, polluted though it is, is not as outright dirty in cities as it was in the era of King Coal.
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vdinets
I know about peppered moths. The thing is, nobody knows how the moths know which morph they belong to. Experiments have shown that they do choose matching backgrounds (when available), but they can’t see their own wings.
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Farnborough John
The most likely selection mechanism for melanism being more common in night-hunting cats is simply that black cats would be more visible in daylight and would therefore hunt less effectively: so that black cats “preferring” night hunting would have increased breeding success. No self-awareness of their colour, or direct genetic link to activity pattern is necessary to achieve this. Just the operation of the laws of statistics.