No, it's not a musty anything!
No, it's not a musty anything! Mustelid is the word, and I'll bet some of our readers know what it means? Let's find out. We'll start with a little quiz, a quick multiple choice question. Here goes.
QUESTION: What is a Mustelid?
A. A poisonous gas from World War II
B. The cap that screws on top of a mustard jar.
C. A rare tropical disease where the eyelids get moldy and smell like old socks.
D. A family of mean, stinky killers.
E. The self-appointed President of Algunistan.
F. All of the above.
G. None of the above.
Isn't this a great quiz? You don't even have to turn to page 87 for the answer. You get it right here. A is definitely wrong. If you're an infant, B is correct; if you're over 3 years old it's wrong. C and E are remotely possible. Therefore neither F nor G can be correct. This leaves D as the only 100% correct answer.
"Big deal!" You say. "So what if mustelids are a bunch of stinky killers? What does that tell me?"
You have a point there. How about this? If you live in Europe, Central Asia or North America, you've probably heard of the badger and the weasel. If your from Africa you've heard of the ratel. If you're from Alaska or Canada you know of the wolverine. And everyone has heard of the mink, skunk and otter.
"Who cares!" You say again. "We're in Costa Rica. We already know about minks and badgers. We want to know about the tropics. What do mustelids have to do with the tropical rainforest?"
You're right again. What about Costa Rica? More specifically, what about mustelids in the southern Pacific slope, where we live? Out of about 70 species of mustelids worldwide, seven are found in Costa Rica, and we have six of those in our own back yard. This is particularly interesting because, although relatively unknown, as a group there are more mustelids in our area than any other carnivore. Other families of carnivores found in our region include one canid (dog family,) five procnids (raccoon family) and five felids (cat family.) If the jaguar someday migrates back to our region via the Path of the Tapir Biological Corridor, the cats will then be equal to the mustelids in number of species.
"Yeah, yeah, yeah," you say, "you still haven't told us about mustelids."
All right, here goes. I said we have six mustelids in our area. Here they are: the long-tailed weasel (Mustela frenata,) tyra (Eira barbara,) grisón (Galictis vittata,) striped hog-nosed skunk (Conepatus semistriatus,) hooded skunk (Mephitis macoura,) and river otter (Lontra longicaudis.)
"You've got to be kidding. What kind of family is that? What do weasels, skunks and otters have in common, and what on earth are a grisón and a tyra? And another thing, you said that mustelids are killers. I know that skunks smell pretty bad, but I've never heard of one stinking anything to death."
Okay, you have a point, but slow down. Let me take your questions one at a time.
First let's see what this oddly diverse group of mammals, called mustelids, have in common. For starters they all have five toes on each of their four feet. They all have well developed anal scent glands, which, as you mentioned, has been carried to extremes in the skunks. They have very keen senses of hearing and smell, but they got short changed in the visual department. They sleep and raise their young in burrows or hollow logs. Although classified as carnivores, most tropical mustelids also eat fruit, the otter being the sole exception.
Mustelids are generally known for their ferocity. Some of them are capable of killing prey much larger than themselves. They typically kill with a powerful bite to the back of the neck. Here skunks seem to be the exception, but even they regularly kill small vertebrates and birds. The otter is invincible in the water, and is a very agile killer, but doesn't reek like the others, presumably because of its watery habitat. The most typical mustelids are the weasel, tyra and grisón, all of which are adept stalkers and hunters that fully live up to the stereotype of the stinky killer. You probably already know about weasels, but lets have a closer look at the other two.
In more than 30 years of living in this region I have seen only nine grisóns, four pairs and one single. I know many local people who have never seen one and don't know what they are. Those who have seen them usually don't know what they are called. Those who do, call them "musas." The grisón is considered rare and very little is known about them. Their scarcity has earned them a place in the CITES Appendix III, which protects them internationally, and they are also afforded protection under the Costa Rican endangered species law.
The grison's appearance reminds me of a badger, only much longer and sleeker. Its body is mostly black to dark gray with a white stripe across the forehead and back to the shoulder. An adult weighs about 3 kilos, is half a meter long and approximately 20 centimeters high at the shoulder. Notwithstanding its small size, the grison's manner reeks of arrogance, not unlike that of a bully who knows that nobody will mess with him.
When we first built the cabins at Hacienda Barú, we made it a practice never to mow the patch of lawn between the cabins and the restaurant. The weeds prospered there attracting many small seed eating birds, to the delight of our visitors. One morning a guest arose at 6:00 AM to go birding. When he walked out the door of his cabin he encountered a grisón sitting in the middle of the driveway eating a rat. Oblivious of the surprised man the mustelid devoured the rat with great relish and sauntered off into the weed patch. The next morning the grisón repeated the performance at the same time and place. By the third morning most of the guests were sitting patiently on their front porches at 6:00 AM for show time. They weren't disappointed.
The short-legged, slinky killer came ambling out of the undergrowth, on schedule, carrying breakfast by the back of the neck. This is the only solitary grisón I've seen. It kept up this ritual every morning for ten days and then disappeared. Presumably it finished off all the rats in our weed garden and moved on to better hunting grounds.
I once saw a pair of grisons run across the road. I was a little surprised at their haste, because they normally strut around as if they own the whole world. Upon approaching I saw the reason for the hurry. The pair were pursuing a large green iguana (Iguana iguana) half as long again as either grisón, and a little heavier. As I approached to within 10 meters, one grisón hid in the underbrush, but the other had caught the iguana by a back foot and wasn't about to release its bite just because some human was approaching in a car.
The iguana reacted to the situation by playing dead. This ploy will usually fool a dog, who will drop the catatonic reptile and lay down beside it to pant basking proudly in the afterglow of success. The moment the dog glances the other way, the iguana is off and up a tree. The grisón however, was much too smart to fall for this ruse. It pulled back on the iguana's foot with a quick jerk, released its bite and immediately lunged forward clamping its sharp teeth into the iguana's thigh. The next bite moved forward to a front leg and the third one went for the kill, deep into the side of the iguana's neck. The whole maneuver took less than ten seconds.
The grisón dragged the dead reptile back into the underbrush to share with its mate.
The grison's close cousin, the tyra, known locally as the "tolomuco," is an equally intelligent and agile hunter, with the advantage of being an excellent climber. Unlike the grisón, the tyra is very wary of humans and quickly runs for cover upon detecting one. These sleek mustelids, about twice the size of a large house cat, are often seen running across the road, but usually all you get to see is a black streak. A farm yard is another good place to catch a glimpse of one. The tolomuco has a bad reputation as a chicken killer, and will often approach houses where wandering fowl may be found.
I once had the good fortune to observe three tyras playing in the top of a tall tree. The base of the tree was rooted well down the hill from my ridge top position, putting the crown at about my level and around 20 meters away. For 15 minutes the three mustelids were unaware of my presence. Eventually the breeze changed and the tyras caught my scent. Their demeanor changed abruptly from playfulness to full alert. Frantically they searched for the source of human scent. One walked cautiously out on a long branch directly toward my position finally spotting me with only 10 meters of thin air separating us. The tyra bared its teeth and snarled audibly, an unmistakable warning. The others started down the tree. I stared in awe as they went head first down the tall straight bole of the lechoso tree (Brosimum utile.) Once they reached the ground the tyras quickly disappeared into the jungle.
Pedro Porras, a veteran guide at Hacienda Barú National Wildlife Refuge, once came across three tyras attacking a two-toed sloth (Choloepus hoffmanni.) "The sloth was torn up pretty badly and bleeding," relates Pedro. "The three tolomucos were trying to reach him, but he had escaped out onto a long hanging vine where they couldn't get to him."
Since the tayras, climb with catlike claws, they were unable to follow the sloth out onto the vine where it could easily cling with powerful, grasping nails. These tyras were so intent on reaching the sloth that they were oblivious to the group of visitors and their guide. The human observers stood watching and photographing the spectacle for about 20 minutes. Pedro described the sloth's wounds as extensive and speculated that it probably eventually died from them.
Pedro seems to have an affinity for tolomucos. On another occasion he called one up to within 4 meters of a group of visitors. He says, he's not sure how, but that he just tried to imitate the huffing, hissing sound they sometimes make, and the tyra walked right toward the motionless humans, stared at them for a few moments and then fled.
The presence of six mustelids, and eleven other carnivores, in this region is a clear sign of a healthy ecosystem. Meat eaters are the top of the food chain and only a well balanced environment will support a large enough prey base to keep their populations stable. If the carnivore's needs occasionally clash with those of humans, we should learn to be tolerant. If a tolomuco kills your chickens, maybe you should build a pen. We humans are arguably the most intelligent animal on earth and are quite capable of inventing ways to protect our domestic animals without destroying the wildlife. Mustelids probably kill many more rats than they do barnyard fowl. A chicken now and then is a small price to pay for the rodent control service provided by the tolomucos and grisons. Remember, the mustelids were here first. We are the invaders and should always respect our natural environment and look for ways to live in harmony with it.
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