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Friday, February 17, 2017

Mammal Course - Class #1 Taxonomy & Evolution

Our 2017 "Conservation Course" started February 6th with an introductory class by David Moskowitz.  Below are notes taken by Avery Young.

Learn more about the Mammal Course here

Class #1 -Mammal Taxonomy & Evolution with David Moskowitz, Feb 6 2017

Watch and listen to the entire class on this video

Our common ancestor
Many talk about the process of evolution as a beautiful progression from something inferior to some form of excellence. The truth is, it’s a lot more complicated and messy than it often appears. For example, when looking at an evolutionary tree of mammals, Cervids (a family that includes deer and elk) appear to be more closely related to Cetaceans (an order of aquatic mammals that includes dolphins and whales) than to horses. Scientists do their best to piece together the evolutionary history of the past 3.8 billion years, but there is much they do not yet know.

It is impossible to study evolution without also studying ecology. The two are closely intertwined. It turns out, the type of environment an animal inhabits determines how successful (or unsuccessful) that animal will be.

Mammals have been around for roughly 160 million years. They evolved from a shrew-like reptile of the “Synapsids” clade. Early mammals had a large brain, good smell, and were nocturnal. It wasn’t until the dinosaurs went extinct 65 million years ago that mammals were able to become super successful. The fall of the dinosaurs meant far fewer predators for the mammals and many more niches (ecological homes) for the mammals to carve out. With the abundance of resources available, mammals began to increase in size and stature, which also contributed to the diversification of this class of animals.

Although mammals can be large and successful, and the class is diverse, it is worth noting that there are still only 5,400 different species alive today. Compare that with the nearly 9,900 species of birds that exist, and a known million species of insects. Mammals might not be the most abundant class of animals, but they are arguably the cutest (as proven by the pika on the left).

Diet plays a major role in mammal diversity and success. Mammals are either herbivores, carnivores, or omnivores (animals that both eat meat and plants),  Wolves are obligate carnivores which means they just eat meat. However, wolves do have something going on in their digestive tract which allows them to occasionally eat berries or other plant-based food. (Cats on the other hand have lost all ability to digest any plant material). Bears are one of the few animals that eat some of the stomach material of ungulates in order to obtain certain bacteria that will help them digest plant material.

Social organization plays a key role in mammal evolution. After all, why are mountain lions solitary but bears much more tolerant of each other?  Mountain lions only seek each other out at certain times of year to breed. Female mountain lions have to “cat call” in their mate to breed with them. So if you see multiple mountain lions together, it’s probably a mom with kittens.  Wolves, otters and ground squirrels are great examples of social mammals.

One of the tenets of biology is that form begets function. For example, badgers have evolved over the millennia to dig with their claws. Skulls and dentition can give us many clues as to how an animal makes its living. For example, carnassial teeth are for gripping prey and shearing meat. Evolution has selected for certain types of teeth which has helped those animals become successful. (BTW…if you haven’t found a tooth yet in the wilderness, keep looking, Dave says they’re everywhere!)

what type of foot structure does this chipmunk have?
Limb structure can also tell us much about how an animal makes its living.  Digitigrade dogs walk on their toes; they are carnivores and need to be fast runners as well as be able to tear apart their meal using their claws. Plantigrade bears (and humans) walk on the flat of their foot, and deer have unguligrade limbs where only a hoof (the tip of one or two digits) hits the ground, making them very fast runners.

Sexual strategies of mammals include monogamy, polygamy and polyandry. Monogamy is the least common. Sometimes wolves will be monogamous. The most common mammalian sexual strategy is polygamy (males breed w/ multiple females). Polyandry is the third mating strategy, which involves one female mates with multiple males. However, this is quite rare in the mammal world.

What makes a mammal a mammal?
  • the characteristic many of us don’t know is that they all have three special middle ear bones
  • they are all endothermic (warm-blooded)
  • they all have hair (some have very little, or only at birth)
  • they all have mammary glands
  • birthing live babies isn’t actually one of the characteristics though it is shared by nearly all mammals. There are some mammals who lay eggs (remember the platypus!!).
Dolphins? Do they have hair? The answer is ‘yes!’ Dolphins have hair on their rostrum (snout or beak) when they are first born.

Methow Valley Orders of Mammals
- Soricidae Family (shrews) have poison ducts on their sharp teeth which helps them do battle with scorpions. If these guys were the same size as mountain lions, we would be scared to go outside!
- Talpidae Family (moles) are also insectivores. We have the pacific mole here in the valley.
Townsend's Big-Eared Bat in the Methow

Bats: are the only true flying mammal; the species in the Methow are carnivores though some bats in the world specialize on fruit.

- Ochotonidae Family includes our pika, the cutest mammal on earth
- Leporidae Family is rabbits and hares   
*Difference between rabbit and hare? One is that rabbits are born altricial and hares are born precocial, fully furred and active (ready to move right away like deer)

Rodentia (largest order in terms of numbers of families and species) - 9 families that include:
A Hoary Marmot is a Rodent
        Pocket gophers
        Squirrels, chipmunks, and marmots
        Jumping mice
        Pocket Mice
        Deer mice, voles, muskrat, packrat
        Old World rats and mice
        Mountain beaver (not a type of beaver)

Artiodactyla (even-toed ungulates)
- Cervidae Family includes deer, elk and moose
- Bovidae Family contains our mountain goats and bighorn sheep
(Pronghorns, which we have in WA but not in the Methow, are in the Antilocapridae family)

Our Methow families of carnivores (which will take two of our six classes!) are Felidae (cats), Canidae (dogs), Ursidae (bears), Mephitidae (skunks) and Mustelidae (weasels, martin, mink, badger, otter, wolverines…).
    Humans are the only species in the Methow!

(See the list of "Mammals of the Methow Watershed" by Dana Visalli here)

The relationship with other species of mammals is hardwired into our brains. Whether you like to hunt, ride horses or treat your dog like a family member, we all have a kinship with other mammals. We have evolved to share connections with other species. We are in the middle of the 6th mass extinction event which is affecting mammals in a critical way. Unlike past extinctions which were caused by asteroids or volcanoes, this mass extinction is being caused by humans. What can we do to change the trajectory of the path we are on?

(All photos ©Mary Kiesau except the bat which is by Kent Woodruff)

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