IMGP1854Tolsenand skulltray
We can learn a great deal from the skulls of mammals, their dentition speaks volumes about their lifestyle!

Here is an abbreviated account of our excellent and informative Feb. 9th Mammals Workshop with the Louisiana Master Naturalists Northeast plus some recent images of mammals taken in various locations in Northeastern Louisiana. 

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We met our instructor, Dr. K. Tolson on the steps of University of Louisiana Monroe’s Hanna Hall. This is also the site of the Natural History Museum with giant prehistoric whale skulls, Zeuglodon, image below! This museum is well worth a visit!

Professor Tolson is a lively, friendly lady with reddish ginger hair and a witty turn of mind. Her specialty is physiology and she brandishes a beaver stick for her pointer in lectures. Quite a character! She enjoyed our field trip very much and expressed a desire for further adventures. I think we’d like that very much.

We enjoyed both her lecture and the field trip very much. We were in Rm. 250 and were greeted with an intriguing sight of boxes of skulls laid out upon the desks. The back row of desks was covered entirely with animal pelts ranging in size from Red and Grey Foxes at the left end to tiny shrews on the far right. There was also a Louisiana Black Bear’s skull (Ursus americanus luteolus).

The class began with an outline of the form of the lecture which wouldn’t dwell so much on the characteristics and phylogeny ( family tree ) of mammals in general but more upon some of our local mammalian fauna with comparisons of particular creatures to help us understand their distinctive nature. She started us off with a visual identification quiz in which I scored 41 out of 50. Kimmie also scored highly!  I think most of us were pleasantly surprised to find out simultaneously how much we knew and the sort of things that we didn’t know.

Squirrels' sign can include gnawed antlers! Louisiana Master Naturalists Northeast examining squirrel sign.
Louisiana Master Naturalists Northeast examining squirrel sign. Squirrels’ sign can include gnawed antlers!

We learned that Mammal studies rely mostly upon sign, rather than observation. This is because many of them are hardly seen because they are secretive and many are nocturnal. Sign takes the form of marks upon the ground and vegetation, scat (poop), food remains and actual animal remains. The skeletal remains are distinctive and of these the dentition (teeth) are very characteristic . Take a house cat as a familiar example and seek its dental formula on the Internet, think a bit about how it uses those teeth. You’ll probably have been toothed by its fangs (I), and seen it grazing grass with its carnassial teeth (P) and crunching its kibbles with its molars (M). Very clearly its teeth serve a different purpose than its prey, a mouse, which as a rodent has teeth best suited to its own lifestyle of chewing and gnawing.

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Canis latrans, a beautifully prepped Coyote skull with impressive dentition.

We learned that each mammal has evolved a specialist set of teeth for their lifestyle. We were introduced to diastema and alveolus and dental formula for each creature we studied. There wasn’t time to study all of Louisiana’s mammals in detail, the selection of mammals that we studied was very suitable! Possums, Squirrels, Armadillos, Beavers, Nutrias and Muskrats and Foxes. I shan’t share all the amazing things that we learned, but rest assured we learned far more than I thought there was to learn about these creatures and our walks in the wilds have been transformed by our better recognition of the signs.

With two or three students to a tray, we eyed up and tried to guess the skulls in our trays. Dr. Tolson illustrated dental formulae first with a coyote skull (Canis latrans), ours was polished like ivory and truly a thing of beauty. Then she showed us the skull of the Virgina (O)possum Didelphus virginiana known colloquially locally as a ‘Grinner’. As omnivores they have 50 teeth! The scariest dentition I’ve seen since my visit to the dinosaur museum downstairs. This reflects their very varied diet, they eat fruit, worms, insects, fresh meat, crustaceans and carrion. Don’t chase them out of your yard, they can eat 5000 ticks per year and are major allies against Lyme disease and other tick fevers.

With teeth like this they can of course, bite their way out of a considerable amount of trouble; when over-faced however, they will faint and ‘play possum’. This is an involuntary loss of consciousness akin to fainting that serves them well when faced by predators that don’t eat ‘sick’ animals, but is hopeless in the face of dogs, sadly. We saw one in our bathroom at Crawfish Springs that looked like it was having a stroke. Kimmie extricated it with a gauntlet and a toilet seat cover. It very slowly curled up on the back porch — clearly a dead ‘un. Later it was nowhere to be found. Resurrection!

Kimmie extricating the Virginia Possum. C. Paxton image and copyright.
Kimmie extricating the Virginia Possum. C. Paxton image and copyright.

Possum Valley in Arkansas has a Possum Festival. Our neighbor old Morris used to trap them, I don’t remember him saying he ate them, but their fur is not valued so … I expect he had ‘em for supper. Apparently they are eaten by some folk, but aren’t sought out a great deal, and their flesh is likened to squirrel.

On the subject of squirrels, I was impressed to learn that there are three true squirrels in Louisiana! That’s not including the flying squirrel.

All three are shot for the pot and traditionally they feature in stews. Our maternal grandmother in Cumbria had an imported grey squirrel fur throw dating from Victorian times that was very soft and warm.

A pretty Chuckledhead or Eastern Fox Squirrel (Sciurus niger).
A pretty ‘Chucklehead’ or Eastern Fox Squirrel (Sciurus niger).
Eastern Grey Squirrel (Sciurus carolinensis)
Eastern Grey Squirrel (Sciurus carolinensis)

The Greys are known colloquially as ‘Cat squirrels’, are faster and nimbler and have white belly fur and white fringed ears and tails. When angry they will cry out a petulant “Fraaaaank!” with a rising tone.

They are attractive little critters and their nests and antics add much interest to the forest, they serve to plant many nut trees from concealed cached nuts and so perpetuate their food trees. They in turn feed hawks, Great Horned Owls, rat snakes and rattlesnakes, bobcats and foxes. Also people! My father-in-law says they taste great with gravy!

 

Which squirrel is this?
Which squirrel is this?

Can you identify the above squirrel? Hint: this photo was taken in northern Louisiana not Atchafalaya.

We went on to study Dasypus novemcinctus! The Nine-banded Armadillo, very delightful but an invasive species considered outlaw in Louisiana but that also has the distinction of being a major predator of invasive Fire ants. Amongst a good deal else, we learned that these are homodonts!

Armadillos are remarkable mammals and also eat fire ants!
Armadillos are remarkable mammals and also eat fire ants!

As mentioned before, they are homodontic, each of their 28 peg-like teeth is a molar, for crushing their ants, termites and earthworm prey. They can be active day or night. We’ve seen them rooting about for their food solo, in pairs and even in a group of three siblings in Tensas River NWR. Each armadillo is born one of four identical quadruplets due to  monozygoticpolyembryony! So they must have lost a sibling somewhere along the way.

Armadillos remind me of the clangers! This pair are at Monroe's excellent Louisiana Purchase Gardens and Zoo. Well worth a visit!
Armadillos remind me of the clangers! This pair are at Monroe’s excellent Louisiana Purchase Gardens and Zoo. Well worth a visit!

 

They are great diggers and we often encounter their burrows in the forest. Their rear feet track over their forefeet and their scat is fragmented into small square ‘tootsie roll’; droppings. We have approached close while they are preoccupied with feeding!

 

They taste better than possum apparently (we have heard of them referred to as possums on the half-shell) but I wouldn’t eat one because they’re so sweet and they also harbor the bacteria that cause leprosy. On that note, they have a special relationship with ULM we learned because a lot of research into leprosy a.k.a. Hansen’s Disease has been conducted here, and it was here that the connection was first discovered. Even so, 95% of us are immune to the disease even if exposed to it. There is a very low incidence of transfer thankfully.

In September they tend to plough through people’s flower beds and the best way to discourage this is to avoid watering during the period according to Dr. Tolson.

Rodent tooth in a Bobcat's scat. C.Paxton image and copyright
Rodent tooth in a Bobcat’s scat. C.Paxton image and copyright

Next we learned a parcel of interesting facts about the rodents of the waterways. The Beaver (Castor canadensis), Nutria (Myocaster Coypus) and Muskrats (Ondatra zibethicus). The beaver and nutria look very similar to each other, other than their tails, but the muskrat is much smaller and Kimmie and I have never seen one nor its nest.(Click here to view an award winning shot of a 12 foot alligator dining on a muskrat by Louisiana wildlife photographer Bob Rogers )

All three species are superbly adapted to aquatic life, Dr. Tolson told us they can all close their lips behind their orange, iron-fortified incisor teeth to enable chewing underwater! We have Coypus in East Anglia and Beavers in Scotland. So this fairly relevant stuff in UK too.

They are all very characterful creatures and they all would brighten your day with an encounter, though as with other mammals, often it is the sign that we see rather than the critter itself. We’ll begin with beavers as they have the distinction of being America’s largest and heaviest rodent and most widespread (from the northern tree-line to northern Mexico) and are admirable ecosystem engineers. They are famous for their work ethic and build two structures that are distinctly recognizable: their nests which are called lodges, are glorious piles of sticks and their dams which are built of felled trees, gnawed branches and packed clay. The Twin Cities (Monroe and West Monroe) have the distinction of having urban beavers in residence in Bayou Desiard, Black Bayou Lake, Russell Sage WMA  and in Restoration Park.

Beaver watching at West Monroe's Restoration Park. This former gravel pit was used as a rubbish dump and then restored to a beautiful park. It has two beaver lodges and a long dam that runs the length of the boardwalk bridge!
Beaver watching at West Monroe’s Restoration Park. This former gravel pit was used as a rubbish dump and then restored to a beautiful park. It has two beaver lodges and a long dam that runs the length of the boardwalk bridge! C. Paxton image and copyright.

There may be others as well, but you can certainly see their sign in the aforementioned places, with the largest and most accessible dam being a major feature of Restoration Park in West Monroe. They prefer water bodies with muddy bottoms: irrigation ditches, ponds, sloughs (pronounced ‘slews’, and bayous. They enrage some land-owners by felling trees and flooding areas and some municipal bodies by blocking culverts but as keystone species they do a lot of good too and are considered assets by many, especially out in the more arid west.

Wood ducks and beaver at West Monroe's Restoration Park. Kimmie Paxton image and copyright.
Wood ducks and Nutria Rat (Myocastor coypus) at West Monroe’s Restoration Park. Kimmie Paxton image and copyright.

Their fur was much sought after for its excellent qualities, and they have been trapped since colonial times for it and also for Castor oil and castoreum scent which was used as a perfume base. They eat bark and we were thrilled to see a beaver slide and chewed beaver sticks on our field trip to Russell Sage WMA with Dr. Tolson.

We found a young beaver’s skull too, on our walk and it was good to see the massive, rootless incisor teeth that perpetually grow. I put a brass cartridge case on my beaver stick for a ferule. It makes a nice walking stick.

We learned that beavers have glossy guard hairs and a dense waterproof under-layer, they have dexterous fore-paws (each a manus) 2 inches long and webbed hind feet (Pedes) 6 inches long and a very characteristic broad flat tail which serves them in swimming, as a ‘sit-upon’ and also to slap the water in a loud warning splash to scare off predators. We can attest that this sudden explosive splash is very loud and disconcerting. It was used against us in Bayou DeL’outre once while we were kayaking.

Professor Tolson also taught us that Beavers are a keystone species because they deliberately work to make dams that create still ponds for their own defense. There is only one entrance to their lodges and that is only accessible underwater. This protects their whole family. Many other creatures (fish, turtles, frogs, otters, waterfowl, fishermen etc.) use their ponds . What is more, frogs, turtles and muskrats are known to overwinter in their lodges! We learned that there are island and bank lodges. Bank lodges we learned, are the equivalent of economy housing, with holes leading into the bank. Black Bayou Lake National Wildlife Refuge has a bank lodge in Bayou Desiard near the old plantation cemetery.

Characteristic beaver sign! C. Paxton image and copyright.
Characteristic beaver sign! C. Paxton image and copyright.

Beaver sign includes footprints and scat and chewed bark and gnawed stumps that look a bit like sharpened pencils. Seeing the planar facets on a tree stump makes you appreciate how tough their teeth must be and how dedicated the little lumberjacks are! Sadly felling trees is dangerous work and sometimes they are found crushed beneath a tree that fell the wrong way. You can also look out for scent mounds beside the water. These are distinct earthen mounds upon which they place their castorum scent to mark their territory.

If land-owners want to move a beaver off their land it can be done non-lethally by the use of scent-marking the mounds with castorum from a road-killed male.

Male Nutria call out to each other. In a fine slough off Corney Creek we first heard quite a terrifying bellow and were greatly relieved to see that it came from a relatively small rodent! C. Paxton image and copyright.
Male Nutria call out to each other across the swamp. In a fine slough off Corney Creek we first heard quite a terrifying bellow and were greatly relieved to see that it came from a relatively small rodent, not one the size of a cow! C. Paxton image and copyright.

Nutria or coypu are imported intermediate-sized aquatic rodents with naked rat-like tails and the aforementioned infra-orbital foramen. Myo in Myocastor means mouse-like. Their spoor is distinctive in that their rear foot is webbed and shows four toes, in their fore-feet their fifth toe never tracks. They are good swimmers and prolific breeders if sufficient food is available. Their teats run along their sides and the young suckle from the sides, fueling a myth that the teats are on their backs.

Their development is so precocious that young may swim, dive and eat vegetation within 24 hours of birth! They consume 25% of their body weight daily. They’re weaned within 4 weeks and are making their own families within 8 weeks.

They were imported from South America to Avery Island by Mr. McIlhenny of Tabasco sauce fame in the 1930’s for their fur-bearing potential and to help clear invasive aquatic vegetation. A Japanese chap had imported beautiful but highly invasive water hyacinths some time before. A big hurricane freed the coypus in the 1940’s and the fast-breeders  became invasive, despite being good alligator and Cajun food. They also taste like squirrel apparently.  Up until the late 1970’s their fur was very valuable, but change in taste and spoilage of wild pelts from burrs from wild Bidens laevis flowers killed off the trade. The Bidens burrs get caught up in the fur and they spread Strongyloidiasis in which larvae burrow under the skin causing ‘Nutria itch’ and skin pustules that ruin the value of their fur. The domesticated ones can be treated with steroids, but the market value of their pelts doesn’t warrant it. Now their $5 tail bounty is worth more than their skins. There’s a price on their tails because they chew off the basal parts of marsh vegetation and so denude the cover and further speed coastal erosion with their burrowing activities. They are tough characters and out-compete muskrats where their range overlaps.

If you can’t see their tails, it is difficult to distinguish beavers from nutrias and I’m never really sure if I can’t see their tails. Nutria are more diurnal and less shy so are more likely to be visible in daytime. They have white muzzle fur and swim higher in the water. Comparing their skulls is a ‘dead’ give-away because the nutria have large holes beneath their eyes called infra-orbital foramen where the cheek muscles (the masitas) attach.

The last of the aquatic rodents is probably the sweetest as well as the smallest, the Muskrat (Ondatra zibethicus). They moved into Louisiana from Arkansas in the 1960’s and the clearest sign of their presence is their nests of cut reeds. These rodents only cut reeds and grasses, never chew sticks. Their manes have stiff hairs that act like webs to assist swimming and their pedes are mildly webbed and also have stiff hairs. Their tails are laterally compressed to assist in steering. They have 16 teeth in total and key-hole shaped infra-orbital foramens. They are present in a small population near Monroe. God bless them!

Foxes are very infrequently seen here. Only once have we caught sight of a brushy tail disappearing from our sweeping headlights. We’ve picked up several on our trailcam ay Crawfish Springs and they’ve always been a bit of a speed blur! Like the possums, they are always about their business!

We learned that the Red Fox Vulpes Vulpes is the larger of the two that occur here, weighing in at up to 18 lbs and leggier than the Grey Fox. It has more pronounced cranial ridges and a white tip to its brush. Prof. Tolson informed us that these foxes favour open areas and are out-competed by coyotes. Where you find the coyotes, you won’t find this fox.

The other fox, the Grey Fox, Uracyon cinereoargentius can also occur in a silver colour form that is very pretty. You can see one in Monroe’s zoo. Prof. Tolson told us that it is shorter and stockier than the Red Fox and is an adept tree climber. It can rotate its shoulders and front paws to ‘hug’ trees and climb high up into the canopy in pursuit of grapes and young squirrels and fledgelings in nests. They can shin up 50 ft and hop lithely from limb to limb. As they forage at different levels the foxes can coexist together happily and the Greys can also coexist with coyotes. The Grey Fox is more of a woodland animal and is omnivorous. They’re partial to sweet potatoes! Their dental formula is 1/1,3/3 1/1 4/4 2/3 = 42 .

The rabbits have 8 species in America but come in two varieties here in northern Louisiana. They are not rodents, but have their own order Lagamorpha. We have the Eastern Cottontails Sylvilagus floridianus which are larger and have darker facial fur and larger-looking eyes, are expanding their range and the Swamp Rabbits Sylvilagus aquatica which are smaller and have cinnamon fur on their faces and necks, that are declining.

>To keep them light on their feet and fast, all rabbits have a fenestrated maxillary bone  in their faces. The cottontails have a hole in their supra-orbital process (brow bone) while the Swampers have a fused brow bone. At Crawfish Springs we had different rabbits in the different areas. North rabbit was an Eastern Cottontail and Southwest Rabbit a Swamper.

Next our lecturer compared American Mink (Neovison vison) skulls with Striped Skunk (Mephititis mephitis) skulls. They used to be both mustelids,  they are very similar but now skunks have their own order, the Mephitidae because of a nipple on their scent gland. This skull comparison gives you an idea of how tough as predators the skunks really are. We have seen two Minks, one crossing the road fast on the way to Crawfish Springs and one on the spit of land favoured by fishermen on Lake D’Arbonne. We have smelled skunks at Crawfish Springs but not seen them there. We tend to just see them dead by the roads, but live ones feed on Kimmie’s mum’s dog and cat food. Little Bit the Chihuahua occasionally gets sprayed as he well deserves!

In Mink skulls the hard palette extends beyond the last molar, the auditory bullae are greatly extended (mink have very acute hearing) and they have a sagittal crest where the jaw muscles attach to give more bite pressure.

A nice factoid about striped skunks is that their white patches are unique, no two are identical. Under their white hair their skin is pink and under the black it is grey. Some people remove their glands surgically and keep them as pets.They are rather gorgeous!

Sadly spotted skunks are no longer believed to be present in Louisiana. They haven’t been seen since the 1970’s and were last seen here in the southeastern ‘Florida parishes’.

Prof. Tolson also says skunks do handstands to spray their musk over their heads at you. They can squirt up to 12 feet and their sphincter can squirt from one or both glands. So don’t be lulled if they get your dog first, they could get you second! She advises that you use woollite followed by febreeze to destink because it freshens but doesn’t strip your dog’s coat of natural oils!

Anyway, after this excellent lecture we drove to Russell Sage Wildlife Management Area off Highway 15 to a wonderful place new to us known as the Wet Soil Unit. Very aptly named, there are flooded fields adjacent to the woodland beside Bayou Lafourche. Pretty soon we were seeing mammals’ signs. First was a Common raccoon, Procyon lotor, dropping on the steps of the observation platform. From the platform we could see wildfowl, Blue-winged teals and American Coots. It was cold, windy and drizzley at first but it dried up later, but we were very excited to explore woodland by Bayou Lafourche and see spoor (prints) of Eastern Bobcat (Lynx rufus rufus) and many Common raccoon prints and also White-tailed deer.

One of our members found a Striped Skunk skull and we then walked along a straight path that runs adjacent to flooded fields. A large flock of White-fronted geese flew eastwards. There we found beaver sticks, gnawed trees, a beaver slide, various scats and masses of spoor and Otter slides.

On the way back I found a Bowfin’s armoured head, the rest had been eaten by an otter.  Some other naturalists found a young beaver’s jaws and a rather nice Common Raccoon’s skull.

Dr. Arthur Lyles found a Nuttall’s Oak acorn (Quercus texana )and Water Hickory nut (Carya aquatica).

We greatly enjoyed this workshop and have been looking out for mammals’ sign ever since! Recently at Tensas River we saw a very good lot!

Field exploration with Louisiana Master Naturalists is great fun because with an expert guide like Prof. Tolson and all those eyes seeking things of interest a great deal is discovered and knowledge shared that would otherwise likely be missed. We saw bobcat and other spoor, multiple otter slides, a beaver slide, gnawed beaver sticks, various scats and the skulls of a young beaver, raccoon and a striped skunk!

There are two rabbits in our area, Eastern Cottontails and Swamp Rabbits.

Eastern Cottontail grazing near Antioch, northeastern Louisiana. C. Paxton image and copyright.
Eastern Cottontail Sylvilagus floridianus grazing near Antioch, northeastern Louisiana. C. Paxton image and copyright.
The 'Swamper' Sylvilagus aquaticus, likes water and has cinnamon facial fur. C. Paxton image and copyright.
The ‘Swamper’ Sylvilagus aquaticus, likes water and has cinnamon facial fur. This one is in a ditch beside the Quebec Road, near Tensas River NWR. C. Paxton image and copyright.
American River Otter in the Tensas River National Wildlife Refuge, Louisiana. C. Paxton image and copyright.
American River Otter, Lontra canadensis, in the Tensas River National Wildlife Refuge, Louisiana. C. Paxton image and copyright.
Water Hickory nut or Bitter Pecan is circled in red.
Water Hickory nut or Bitter Pecan is circled in red.

 

An American River Otter likely feasted off this Bowfin, just leaving the armoured head-shield of this 'living fossil'.
An American River Otter likely feasted off this Bowfin, just leaving the armoured head-shield of this ‘living fossil’.
Louisiana Black Bear (Ursus americanus luteolus) can be seen in and around Tensas River National Wildlife Refuge in Madison Parish.C. Paxton image and copyright.
Louisiana Black Bear (Ursus americanus luteolus) can be seen in and around Tensas River National Wildlife Refuge in Madison Parish. C. Paxton image and copyright.
Common Raccoon in the Tensas River at Tensas River National Wildlife Refuge, Louisiana. C.Paxton image and copyright.
Common Raccoon hunting in the Tensas River at Tensas River National Wildlife Refuge, Louisiana. C.Paxton image and copyright.
Eastern Bobcat, Lynx rufus, on the Greenleas Safari drive at Tensas River NWR near Tallulah, Louisiana.
Eastern Bobcat, Lynx rufus, on the Greenleas Safari drive at Tensas River NWR near Tallulah, Louisiana.