Posted by: Rob Viens | July 3, 2013

Sleuthing Darwin’s Deer

With the help of his “new assistant”, Darwin continued to collect and prepare samples throughout the end of June to the point where it became a routine.  On the 28th we wrote:

“My only object is completing the collection of birds & animals; the regular routine is one day, shooting & picking up my mouse traps, the next preserving the animals which I take. — On Saturday I rode some leagues into the Camp & had some excellent rifle shooting at deer; I killed three bucks out of one herd.— My occupations are so very quiet, it gives me nothing more to say, than if I was living in an English village.” (June 20-28)

So what was Darwin hunting on the grassy plains of Uruguay?  Well, to start, here is a description from his Zoological Notebook of the bucks that he shot:

“Are very abundant in the mamillated plain round Pan de Azucar.— Manners resembling those at B. Blanca.— This specimen was shot out of a herd of seven.— The Gauchos say he is nine years old:— teeth all decayed.— Smell intolerably strong & offensive, almost creating Nausea.— this seems to occur at seasons when the Horns are perfect” (Zoological Notebook)

To add to the description, it is also worth noting that in one source (referenced in the Zoology of the Voyage of the Beagle Part 2 (Mammal)) Darwin describes these large mammals as averaging about 60-70 pounds (~30 kg).

Darwin later refers to these specimens as Cervus campestris, however, Cervus (a genus that includes the red deer and sika deer) are not found in South America.  So it appears Darwin was again naming specimens based on the familiar. The ones he collected were New World deer, not found outside of South America.

Uruguay has three species of deer  – the Marsh deer (Blastocerus dichotomus), Gray Brocket (Mazama gouazoupira), and Pampas deer (Ozotoceros bezoarticus). The range of all three species have been reduced over the centuries, however, it is possible that all three could have been found on the plains north of the Rio de la Plata in Darwin’s time.

The Marsh deer appears to be the largest and most extensive of the local deer species. As their name suggests, however, they live in marshy areas – often wading and even swimming in the water.  This, taken with their size (adults 80-125 kg (180-280 lbs)), and preference to be in very small groups (less than 6), suggests this was not Darwin’s target today.

March Deer in Argentina (from Wikipedia Commons):

Marsh Deer

The Grey Brocket is a small deer , with adults averaging about 11-25 kg (24-55 lbs). They typically like to be near the forests edge or in the brush – areas that afford them some degree of protection from predators. These characteristics, along with their preference to be more active at night, make the Grey Brocket and another unlikely candidate for Darwin’s samples.

Grey Brocket in Argentina (from Wikipedia Commons)

Grey Brocket

That leaves us the Pampas Deer, which as it turns out, do seem to be a good match with Darwin’s description of the deer he collected. As their name suggests they tend to live in the lowland grasslands, where they feed primarily on (wait for it…) grass. And they are pretty close to Darwin’s estimated weight, with average weights between about 30 and 40 kg (66-88 lbs).

Pampas Deer in Serra da Canastra National Park (from Wikipedia Commons)

Pampas Deer

But the one characteristic that really “seals the deal” for me is the smell of the Pampas deer. Wikipedia notes that “Males have a strong smell secreted from glands in their back hooves that can be detected up to 1.5 km away.”  Darwin summarizes this characteristic well in Voyage of the Beagle:

“The most curious fact with respect to this animal, is the over-poweringly strong and offensive odour which proceeds from the buck. It is quite indescribable: several times whilst skinning the specimen which is now mounted at the Zoological Museum, I was almost overcome by nausea. I tied up the skin in a silk pocket-handkerchief, and so carried it home: this handkerchief, after being well washed, I continually used, and it was of course as repeatedly washed; yet every time, for a space of one year and seven months, when first unfolded, I distinctly perceived the odour. This appears an astonishing instance of the permanence of some matter, which nevertheless in its nature must be most subtile and volatile. Frequently, when passing at the distance of half a mile to leeward of a herd, I have perceived the whole air tainted with the effluvium. I believe the smell from the buck is most powerful at the period when its horns are perfect, or free from the hairy skin. When in this state the meat is, of course, quite uneatable; but the Gauchos assert, that if buried for some time in fresh earth, the taint is removed. I have somewhere read that the islanders in the north of Scotland treat the rank carcasses of the fish-eating birds in the same manner.” (Voyage of the Beagle)

Dude…maybe it is time to get a new handkerchief. I know you are a long way from home, but I’m sure that you can find a small rectangle of cloth to replace the old stinky one :).

All species of deer (except for the Chinese water deer) have antlers that they lose each year. The Pampas deer is no exception, and Darwin was able to collect several of these antlers this month (he calls them “horns”).

Pampas deer antlers from Zoology of the Voyage of the Beagle:

Pampas deer antler sketch from Zoology of the Beagle

According to George Waterhouse,who wrote up Darwin’s mammal samples for Zoology of the Voyage of the Beagle, it was the antlers that the locals based the animals age on:

“The Spaniards say they can distinguish how old a deer is by the number of the branches on the horns. They affirmed that the specimen, of which figure 4 represents one of the horns, was nine years old.” (Zoology of the Voyage of the Beagle, Part II: Mammals by G.R. Waterhouse)

Sadly, the number of Pampas deer in Uruguay has seen a tremendous decline in the past 150 years, largely due to overhunting . It is these types of changes that make Darwin’s records from the region all the more important to us today. (RJV)

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