13 April 2018

Squirrels - biological research


This week I was helping my husband with his biological research.  Almost a decade ago, the area where we live suffered from the gray squirrel's die-off. The epidemic of mange combined with some viral disease almost wiped off the population. 
Since die-off, my husband is doing regular yearly surveys of the squirrel's populations to see are they recovering at all. 
If I can, I help him. Two persons see more than one. And early morning walks are quite pleasant.
Biology has slightly different rules in data taking than astrophysics. Since most of the qualities they try to measure are following a Gaussian distribution, the first priority is to ensure that data reflect the population as close as possible. Usually, that's accomplished by making the data sample random. However, in this kind of survey, an issue of repeatability is also important. 
The first year after die-off my husband marked 5 different tracks all around the valley. Each year, at the same time, beginning of the April, we go over those same tracks and count the squirrels we see. We count squirrels only on the tracks, meaning if we see a squirrel outside of the track, that one is not counted. 

Why count squirrels?

The whole idea of the project is to catch and track the recovery of the squirrels. The project started optimistically. The first year we detected a family of squirrels in one location and one or two squirrels in others. At the time, they were all healthy, enjoying the bounty caused by the lack of the competition. 
But hopes soon vaned. Since die off, for the last 9 years, the squirrel’s situation is the same. Barely any squirrels, in the best years we saw 10 in total, over the area that covers around 20 square miles. This same area could provide the habitat for around 10000 squirrels. Meaning at the peak of the population one could see few tens of squirrels per one track.
Some years we would see the whole family of the squirrels, and our hopes will perk up. But then, next year, at the same location we barely see one.
This year we got another example of the possible explanation. At the location where we saw a healthy squirrel family last year, this year we saw only one. And that lone squirrel was completely covered in mange. Over the years my husband got reports of the dead baby squirrels, and subsequent necropsy revealed the same mange. Illness is still here.
Yes, it might be that the illness is what is keeping the population down for all these years. I do not know for sure, I’m not a biologist. My hubby is careful in stating anything because he also saw a bunch of squirrels flatten by the vehicles in this same period. And some tracks have only one squirrel. One squirrel cannot reproduce. 
Anyway, the survey is in progress but looks good. In only two tracks we saw 8 squirrels in total, 6 of them in just one track, all adults. But again, this does not mean that population is recovering. With mange still present, it is big question will this year families survive to reproduce next year.


I would also like to include a warning. Before the die-off the population of squirrels in this location was huge, sustained not only by the food they found in the wild but also by countless feeders that almost every resident put up. 
And those feeders are what contributed greatly to the die-off. It takes only one sick squirrel to use the feeder to infect every other squirrel who comes to that same feeder. This particular disease was killing squirrels all around California, spread by squirrels themselves, when they disperse from the original location. So almost decade ago, a sick squirrel came to this mountain valley, and disease spread like fire, thanks to the feeders people put in their yards. 
The best option is not to put feeders up. But if you do, for any kind of animal, then make sure to wash it regularly, with bleach. And by regularly, I mean at least weekly. Unless animals you feed poop at the feeder, then you have to clean it more often.
Just to say, with the biologist in the family we do not have any feeders at all in the yard. Instead, we have plants that can provide habitat. Like milkweed for Monarch butterfly, flowers that can feed hummingbirds, seeding plants to feed another kind of birds, etc. 
This works, we have the most wildlife in our garden than any of our immediate neighbors. So this is what I would recommend you to do if you have a garden of your own and wish to attract some wildlife. 
Mind, some of the wildlife we attracted is rather annoying and I would rather chase them away, but. 

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