M. Jolly-Van Bodegraven
2014
22 March Ashland and Coverdale Farm Preserve, Hockessin, Delaware
15 degrees celsius, overcast (9/10) at 1 p.m. start of trip; clouds opened up by 4:15 p.m. end of trip (3/10), minimal wind
Ashland - secondary forest, riparian and marsh habitat
Coverdale - hillside meadow habitat
As we began our afternoon of searching for mammal tracks and sign, a group of approximately three dozen tundra swan flew past high overhead, moving northwest along the Red Clay Valley. The birds often winter in the Mid-Atlantic but may have been further south (in the Carolinas) this year due to the relatively heavy snowfall in the region this season. Although the objective of the afternoon was to focus on mammals, the charismatic birds felt like a good omen and provided an opportunity for our guide for the day, Derek Stoner, to share some information about another natural phenomenon. The birds may have been heading for Middlecreek in Lancaster County, where they often rest for a few weeks before continuing their journey north, ultimately nesting in the tundra above the Arctic Circle.
The mammal walk itself also got off to a promising start quickly, as a pause by Ashland’s visitor center led to our first mammal sign of the day - a heavily browsed rhododendron. Nearly every leaf below about four feet high had been browsed, showing a rough edge to what remained, indicating they had been eaten by white-tailed deer (Odocoileus virginianus). The portions of leaves remaining were browning, and the stems yellowing. The plant looked quite damaged low, but the higher two feet of the shrub looked healthy. The extensive browsing may have been another effect of the relatively snowy winter, as ground cover would have been unavailable to deer at Ashland for weeks at a time. Continuing on the path past the visitor centers, two holes on the uphill side are evidence of a groundhog (Marmota monax) many in the group know live in the area - we had learned in our lecture Thursday night that the somewhat ponderous looking animals are a species of ground squirrel that can range up to about 12 pounds and 28 inches long, though they often appear heavier to me because of their chunky build.
Just past the holes the group stopped at a crab apple tree with a low, strikingly horizontal branch, which is often an attractive place for squirrels to sit and eat, the tree cover overhead providing some cover from aerial predators. This branch had a midden pile underneath it, and black walnut shells showing evidence of both red and grey squirrels were found. The red squirrels (Tamiasciurus hudsonicus) chew dime-sized holes in the walnut shell, then reach in to get the nut inside. There will often be one hole in each quadrant of the walnut when eaten by a red squirrel. The grey squirrel (Sciurus carolinensis) has larger paws and cannot reach inside the walnut. It will split the shells in half or gnaw away an entire side to reach the nut inside. Although no sign of them was seen, the tree and midden pile also likely attract white-footed deer mice (Peromyscus maniculatus), which would eat pieces of walnut the squirrels overlooked and the fruit of the tree when in season.
Starting downhill, we came upon a deer track and learned some of the information one can gather from a track besides identifying the animal. With deer, the track shows the direction of travel and even the relative age of the deer; their hooves wear over time, meaning the tracks of young deer are pointed and older deer more rounded.
(Later in the walk, just before the marsh down by Red Clay Creek, we found a fresh deer track - distinguished by loose dirt within the track that had not yet settled in. That track also showed the deer’s dew claws, two vestigial toes from a bit higher up the deer’s hoof that only show in tracks on soft substrate and usually when the deer was running.) The first track we found was crossing the trail and showed a game trail - a distinct path through the forest that deer, as well as fox, coyote and others, use repeatedly as the path of least resistance - it follows the terrain, is direct, and is worn down by ongoing use, making it easier to pass.
Next to the deer track was an area of tall grass that had been compacted over the winter, and it showed holes that were entrances to meadow vole (Microtus pennsylvanicus) tunneling. Derek was able to peel back the matted grass - evidence that it is a nonnative species - and revealed extensive tunneling, grass seed spread about, and possibly a nest area the voles could have been using. The tunnels open out into larger areas used as nests or latrines.
We continued on down the path, turning to follow Wildflower Brook up to the campfire site, crossing more deer tracks. As we approached the campfire site, a red squirrel ran down a tree and off into the brush - it would be the only live mammal I would see for the day, but perhaps surprisingly, I found the evidence of mammals - the tracks and sign we found - nearly as exciting. Just the abundance of signs that the land was inhabited by such a variety of animals, and learning what the signs meant, was compelling, encouraging, and fun. Reading the landscape is a bit like reading poetry or other art - it opens up a way of seeing and understanding the world we don’t usually use from day-to-day, broadening our perspective and heightening our awareness of life.
The firewood shed at the Wildflower campfire site showed more evidence of squirrels - a cache of walnuts and clear gnawing on the wood of the structure itself. As with other rodents, squirrels must regularly gnaw on hard wood to keep their incisors from overgrowing. If they don’t, the overgrown teeth curve under and can end up preventing the animal from eating, leading to its death. Although not likely the case at the wood shed, rodents also like to chew on wood frequently handled by humans for the salt deposited by our sweat.
After failing to find any tracks along the brook, we returned down the spur to the main trail, coming across a buck rub on the way. Bucks rub their antlers against trees not to remove the velvet but after that covering has already come off. Rubbing give the bucks practice sparring before they use the same essential motions competing with other bucks. It builds up their neck muscles, marks territory, and deposits their scent, which comes from preorbital glands and forms a central part of the deer’s social system. The trees also stain the deers’ antlers. In Northern Delaware, bucks are primarily rubbing deciduous trees, and their antlers take on a golden brown color. In primarily coniferous forest to the north, deer and elk have dark, chocolate-colored antlers, stained by the tannins in evergreen trees. (Without the rubbing, the antlers are bone-white.) Rubbing continues until the antlers fall off, some time between December and March or April. Antlers are regrown each year, the fastest growing organ of any mammal, adding up to half an inch a day.
We continued on down the trail into the forested area down by the creek. We came across another buck rub that was older - the tree had begun to heal over. The two rubs are shown here.
 |
Above is a buck rub from the current season; to the right
is an example of a sapling healing over a buck rub that
is a couple of years old |
In the same area, we found two squirrel nests high in the trees, nearly at the top. The nests are fairly large collections of leaves and are often found together. These are evidence of grey squirrels, as the red squirrels are more solitary. While squirrel nests provide the animals some shelter, in the winter cold they are more likely to hole up in tree hollows, which provide more protection.
Down along the creek we really began to have more luck with tracks, finding clear raccoon tracks right along the water on a muddy bank. They showed the full, classic “hand” print of the raccoon (Procyon lotor), deeply pressed into the mud. Going the other direction just a bit inshore were a series of prints we could not immediately identify. There were three or four paw prints tightly grouped together in three distinct locations, with about two feet between each group. That configuration and the prints themselves - of five-toed paws about 1.5-inches long - suggested mink (Mustela vison) to some in the group.
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The unidentified tracks occurred in groups about six inches long,
as shown above, and the individual prints were about 1.5-inches.
Though they could be hard to make out, they appeared to have
five toes each. While we did not make a definite identification,
they seemed to be from an animal in the weasel family. |
The shape of the prints themselves look to me like they could have been made by a striped skunk (Mephitis mephitis), and just next to this low muddy bank we found a good example of a tunnel dug by a skunk looking for insects, grubs or bulbs to eat. It was about an inch in diameter and cleanly excavated. (Squirrels also dig, but their holes look messy and often have the removed dirt piled about.) The distance between the groupings of four prints, separated by a couple of feet, is more characteristic of mink, however. Skunks can leave tracks in that pattern, but would only have up to 7 or 8 inches in between groups. Both animals are in the weasel family.
Back to the trail, there was a muddy section that captured the deer print with dew claws mentioned earlier, as well as a couple prints from a fox, which we assume to be a red fox (Vulpes fulva) because gray fox are generally unknown in the area. Although there are many prints from domestic dogs on the trails at Ashland, the fox prints can be distinguished by several factors. They are, generally speaking, smaller - about the diameter of a half-dollar. The toes are not splayed out as typical in dogs’ prints, and the overall aspect of the print is circular.
We entered the marsh proper on the boardwalk trail looking for signs of muskrat (Ondatra zibethicus), one of three aquatic mammals in Delaware’s Piedmont and the only one we were likely to find fresh evidence of. (The others are beaver and river otter, although there are occasionally mink as well.) Although there are no muskrat huts in the marsh at Ashland, the animals are present, probably living in bank-side dens excavated up from underwater to keep their entrances hidden. We saw sign of muskrats in considerable browse of the aquatic grasses beginning to show above the water with the start of spring and in half-tunnels in the dirt under the marsh’s shallow water, akin to those made by the meadow vole on land. Two sharp-eyed members of the group also found muskrat scat, accurately described as looking like a small grey jellybean, on a rock and a log along the shoreline of the Red Clay Creek.
Muskrats are relatively large rodents, with body length of 10 to 14 inches and another 9 to 11 inches of tail. They are the only mammals in our region that have a vertically flattened tail, which distinguish it from the similar but invasive nutria (Myocastor coypus), imported from South America around 1900 for fur. Muskrat historically were a significant species in the fur trade. Delaware’s Leipsic is named after Germany’s Leipzig, which was the fur trading capital of Europe years ago. In addition to their fur, muskrat are also hunted for their meat.
Their fur is dark brown or black in the guard hairs and silvery below, and it is very thick, which traps air to provide insulation and buoyancy. Their tail is naked and black. Muskrat are active at all times of day, though most active from mid-afternoon to dusk, and can be seen swimming through their preferred habitat - marsh with a constant water level, which they prefer between four to six feet deep. When swimming they can be distinguished from beaver because their heads appear wedge-shaped, as opposed to squarish for beavers, and they keep their tail on the surface of the water, which beaver never do.
They live either in muskrat lodges - cone-shaped structures of sticks and mud that are about five feet in diameter at the base and rise up to three feet - or in burrows in banks. In both kinds of shelter, entrances are underwater. Muskrats can stay underwater up to 17 minutes. Whether living in lodges or burrows, muskrats live in large family groups and have definite territories, communicating by scent - their musk - and some squealing and squeaking.
Muskrat primarily eat plants, up to one-third of their body weight every day, but will eat animals, such as mussels, occasionally. They will eat the shoots of grasses, as shown in the photo to the right, as well as roots of aquatic plants. They also eat crops and can be viewed as a pest. They are a food source for a wide variety of predators, aquatic, terrestrial and aerial; the most common threat to them at Ashland would be raccoons.
We were nearing the end of our exploration of Ashland but still saw fox scat - largely made up of hair this time of year, curved and about three or four inches long - and old sign made by beaver (Castor canadensis) a couple of years ago - gnawing on bankside trees near the trail bridge close to Brackenville Road. The Ashland hike ended as it began with birds when deep excavations of a standing dead tree were pointed out as the work of the pileated woodpecker (Dryocopus pileatus), the only one in the area that would drill so deeply into the wood. There was also general excitement over snow drops - the first flowers of spring, which actually started blooming in late winter here - and my happiness at spotting a second wildflower was tempered when others in the group identified it for me as an invasive, lesser celandine, that they said could take over much of the marsh fairly quickly. I’ll be looking at the area whenever I’m back this spring to see how it progresses.
From there we loaded into the van and cars to make the short trip to the preserve side of Coverdale Farm Preserve, a 352-acre parcel of which a bit less than one-third is actually farmed, with the rest either wild and forested along Burrows Run or existing as meadow, part of which is being restored with warm-season grasses and native wildflowers and the rest remaining in orchard grass, which is grown on many farms in the area for use in compost on mushroom farms. The considerably different habitat and the fact that the land is much less intensively used by people made Coverdale a good place to find sign of different animals than Ashland.
We also took a different approach to the search at Coverdale. Whereas at Ashland we had taken a traditional guided nature walk, one after another, Coverdale was a chance to spread out and explore.
This was a great way to cover more of the hillside meadow and meant we found more of what there was to see. Some was a repeat of Ashland, although even in those cases, we were seeing different manifestations of the same phenomena or different sign of the same animals. As you might expect, meadow voles were present at Coverdale as well, for instance, but in addition to holes down into tamped down grass, we saw a couple well-defined tunnels that had become exposed. We also saw a woody plant that a vole had attempted to girdle, stripping the bark low down. The marks of the rodent’s teeth could be seen - paired and about 1/16 of an inch in width. Voles have been shown to impede reforestation through this scarring of woody plants, thus maintaining their meadow habitat.
Walking through the meadow we saw evidence of mammals primarily through their scat, fur and digging. As people found things, the group would gather and pass them around so everyone got to learn. Much of what we found was scat - pea-sized and -shaped droppings from rabbits (Sylvilagus floridanus), fox, probably deer and maybe mice or squirrel. The main animal everyone was eager to find sign of, one we knew was much more likely to show up at Coverdale than Ashland, was the coyote (Canis latrans). Coyote scat was first found at Coverdale in 2007, and the animals have been seen, rarely, by members of the group since. Throughout the afternoon we repeatedly found scat that would indicate coyote, including some at the entrance of what could be a fox den. Coyotes are known to eliminate competition, and until they arrived in Delaware, fox had been the top predator, since black bear were extirpated. The scat at the entrance to the burrow, and some possible coyote fur found within a few feet, probably indicated a coyote sending a message. Since coyotes have moved into Delaware, filling an ecological niche opened by the removal of not only black bear but also wolf and mountain lion, fox populations seem to be declining due to the competition.
The most conclusive evidence of coyote, though, was scat on the trail we found towards the end of the afternoon that contained deer hair and bone fragments, likely pieces of a skull given its thinness. Coyotes feed on animals whole and have the jaw strength to chew up bone, most of which their bodies can also break down. No other animal in the region would have been able to chew up and eat so much bone.
Fur found throughout the meadow also helped identify several species, in addition to coyote, such as fox and rabbit. One area I came across in the high grass must have been the site of a predator catching a Virginia opossum (Didelphis virginiana). You can see in the photo the amount of fur and its distribution. It was probably spread across two feet or a bit more, and the distinctive coloring - white to black to white or silver - identified it as possum.
Possums are North America's only marsupial, the continent's most ancient mammal family, having evolved in the Cretaceous. (Platypus and echidna belong to an even older group, but no representatives of the subclass are native outside of Australia and New Zealand.)
Possums have been spreading across the continent from their original home in the Southeast, aided by human development. In fact, they are so well adapted to living with humans, urban possums are up to a third bigger than their rural counterparts and have higher survival rates, possibly because of fewer predators, although they still typically only live a couple of years. Possums' relative age in our region and north can be inferred from the condition of their ears and tail. While northern populations of possums have thick under fur, their ears and tail are hairless and often frostbitten.
The tail is remarkable for its utility to the possum as well - it is prehensile, nearly as long as the possum's body, and used for climbing, although possums do not hang from their tails as some believe. Possums also have feet well-suited for climbing, with an opposable hallux (big toe).
Possums range from four to 13 pounds and 13 to 22 inches long, although size estimates apparently vary among different publications. They have an average of eight young per litter and up to three litters per year, depending on how far north they are.
The last main type of sign we found was the various digging sites. In addition to the den that was about the right size for fox, we found a mound of earth about a foot long and half a foot wide that could be evidence of moles, although one would expect more of such sign for moles. We found another skunk tunnel, this one bigger than the one we had seen at Ashland. It too could have been made by a skunk searching for insects or bulbs, but being in the meadow, it may also have indicated a skunk finding a vole or even a vole’s den.
Though not a common find, we did come across bone as well, in each case probably from deer. Two knucklebones turned up in different places, one of which was near an “island” of woody snags and brush where the vole had attempted to turn back the new growth. These different habitats are magnets for mammals and predators as places to hide. And in the hedgerow at the far end of the field, a fellow classmate discovered a collection of ribs, vertebrae and other bones near two den-like holes.
List of species found and sign
White-tailed deer (fur, scat, browse, buck rubs, tracks)
Groundhog (burrow)
Grey squirrel (walnuts)
Red squirrel (walnuts, seen running down a tree)
Meadow Vole (tunneling, seeds below grass, woody plant girdling)
Skunk (tunneling)
Raccoon (tracks)
Mink? (tracks)
Red Fox (tracks, fur, scat, possible den)
Muskrat (tunneling, browse, scat)
Beaver (chewing)
Virginia Opossum (fur)
Eastern Coyote (fur, scat)
Cottontail Rabbit (fur, scat)
