This is the time of year when two-year-old beavers leave their lodges and strike out on their own, primarily because the woods surrounding a pond usually can’t support more than one family of beavers. Beavers are exceptionally territorial; once they’ve established a lodge, they do not take kindly to interlopers. In order to make this perfectly clear to house-hunting young beavers, in the spring resident beavers build what are called scent mounds — piles (up to three feet in height, but usually much smaller) of mud, leaves and pond-bottom debris — around the perimeter of their territory. They then smear castoreum, a substance that comes from their castor sacs, over the mound. Chemicals in the castoreum convey to roaming young beavers that this particular pond is spoken for.
“Peeps” and “quacks” fill the air these days. How is it that these frog calls travel so far? It’s all thanks to a thin membrane , or sac, that most frogs have. Note the single inflated sac of the spring peeper, and the paired sacs on either side of the wood frog’s head. These vocal sacs act as resonating chambers, causing the male frog’s mating call to be amplified and carried far (some species of frogs can be heard over half a mile away). Most frogs have one of three basic types of vocal sacs: a single throat sac (the most common), paired throat sacs (partially separated by connective tissue) and paired lateral sacs (completely separate chambers on either side of the head). Vocal sacs are outpocketings of the floor of the frog’s mouth. When calling, a frog closes its mouth and nostrils, and expels air from its lungs through the larynx and into the vocal sacs. The vibrations of the larynx emit a sound which resonates within the vocal sacs. The frog continues calling as muscles within its body wall force the air back and forth between the lungs and vocal sac. The thickness of the vocal sac wall in frogs varies. Typically, small frogs that call in the air (spring peeper) have thin vocal sac walls, whereas those that call in the water, particularly large species (green and bull frogs) often have thick-walled vocal sacs that appear swollen, not inflated like a balloon, when filled with air.
Do you know a 3 – 8 year old who loves animals and would enjoy getting close-up views of the antics of a red fox kit during the first summer of his life? My second children’s book, Ferdinand Fox’s First Summer, has just been published by Sylvan Dell in both hardback and paperback. I have been lucky enough to have had the opportunity to observe and photograph young red foxes as they interact with each other and with their parents. This book consists of a selection of these photographs, accompanied by text and an educational component at the end of the book. Look for Ferdinand Fox’s First Summer in your local bookstore. If they don’t carry it, you would be doing me a huge favor by asking them to. Thank you so much. My next children’s book is on Beavers and will be coming out in the spring of 2014. (I am still looking for a publisher for Naturally Curious Kids!)
Male red-winged blackbirds have returned to Vermont, and their most notable features are the brightly-colored reddish-orange feathers on their “shoulders”, referred to as epaulettes. In the military, an epaulette is a shoulder ornament that indicates, through its position, color, length and diameter, the bearer’s rank. Some birds, including male redwings, also possess this badge, or visual cue, which indicates the social status of the bird to other birds of the same species. Studies of male red-winged blackbirds and their epaulettes indicate (through dyeing their bright orange/red shoulder patches black) that epaulettes play a significant role in the male’s defense of his territory. Over 60% of the redwings that had their epaulettes dyed black lost their territories to other males. Further research revealed that aggression by a territorial male redwing is proportional to the epaulette size of the encroaching male redwing. It also indicated that male redwings intruding into redwing-occupied territories greatly limit the exposure of their epaulettes by covering them with black feathers. (Female red-winged blackbird plumage is brown and lacks epaulettes.)
For the past two to three months, coyote courtship has been taking place. Both males and females have been marking more frequently, and male coyotes have been traveling further than usual in search of a mate. A female has marked the top of the stump in the photograph – you can see the foot prints she made as she squatted to urinate. The blood-tinged urine indicates that she is in estrus, or heat. With luck, you might hear the duet of a male and female coyote that is sometimes sung just prior to copulation.
Even though black-capped chickadees are named for their chick-a-dee-dee-dee winter song, it is their so-called spring song which resonates most with many of us. It seems as if chickadees are immediately aware of when the days start to get longer, as their mating song begins as early as January. Sounding to some like “fee-bee” and others as “hey-sweetie,” this delightful song consists of two whistles, each about half a second long, with the second whistle a lower pitch than the first. Although these cavity nesters won’t actually be breeding until April, we will continue to be serenaded by their courtship song throughout the winter. As birdsong expert Donald Kroodsma so aptly describes this song, “It is the purest of whistles, this promise of spring.”
On the inside of the hind legs of all white-tailed deer are glands called tarsal glands. They consist of a tuft of long hairs coming from an area of skin in which are located glands that secrete a fatty substance. This fatty substance adheres to the long hairs. When deer urinate, they often assume a crouched posture, causing their urine to run over these hairs. The lipid, or fatty material, on the hairs causes some of the urine that runs over them to remain there. Excess urine is licked off by the deer. The combination of fatty material and urine gives the glands a unique smell (not the typical deer urine smell.) During the breeding season mature bucks urinate on the tarsal gland much more frequently, and don’t lick off the excess urine, which creates a distinctive rutting odor . This practice is referred to as “rub-urination.” All deer urinate on these glands throughout the year.
Although Spring Peepers emerged from hibernation about two months ago, on warm nights the males are still advertising for mates and will continue to do so into June. Let your ears guide you to the peepers as they call repeatedly, often while perched on low vegetation near water. Armed with a flashlight, look for the movement of their vocal sacs as they inflate and deflate as the peepers sing.
The welcome sound of the “Morse Code woodpecker” is once again reverberating through our woodlands. Although many woodpeckers drum against hard surfaces with their bills, yellow-bellied sapsucker drums are distinctive — they usually begin with several rapidly repeated strikes in an “introductory roll” followed by a pause, then more strikes in an irregular pattern which some people liken to the Morse Code. These birds, like most woodpeckers, communicate with each other by drumming on different surfaces – often dead snags, but also metal signs and roof tops. They communicate over long distances, so the louder the drum, the better. Males are arriving back on their breeding grounds and establishing territories with the help of this drumming before the females arrive. Females arrive back about a week later than males, at which point, drumming will assist male sapsuckers in obtaining a mate. Females also drum, but less frequently, more softly and for shorter periods of time. Photo is of an adult female yellow-bellied sapsucker.
After noticing the sudden loud clacking chorus at a nearby temporary woodland vernal pool, I went down to investigate, and there were dozens of wood frogs floating on the surface, as they croaked their duck-like quacks in the hopes of attracting female wood frogs. As far as I could determine, they were out of luck on this, their first day at the breeding pool, as I don’t believe the females have arrived yet. One clue was the relatively small size of the floating frogs and it seemed as though every frog was calling (only males call). Plus, time after time a wood frog would swim up to another wood frog and attempt to grasp it only to have the object of its desire utter a “release” chirp (a call made only when a male clasps another male) and swim rapidly away.
I heard my first peeper on March 18th, roughly two weeks earlier than in past years. These tiny members of the treefrog family begin mating rituals shortly after the end of hibernation. The males gather at small pools by the hundreds. Each male establishes a small territory and begins calling the familiar high-pitched “peep” quite frequently. The louder and faster he peeps, the better his chances are of attracting a receptive female. Males usually compete in trios, and the male with the lowest-pitched call usually starts the vocal competition. If you look closely at the peeper in the photograph you can see some snow fleas hitching a ride.
Porcupines leave plenty of signs where they have eaten the inner bark, or cambium layer, of a tree. Bark is missing on the trunk of the tree, leaving fresh, yellow wood exposed, which often bears incisor marks. An observation I have made over the years is that porcupines often de-bark around or near their hollow tree dens. Typically, if a tree den is used year after year, they gnaw off bark each year, sometimes eating the old, scarred portion which, due to previous chewing, lacks cambium cells. This has led me to wonder whether fresh de-barking in the vicinity of their tree den entrance might have more, or as much, to do with a porcupine’s staking out a claim on that tree than with its sustenance. I have never come across any research that even mentions this phenomenon, and would welcome feedback from anyone who has.
If the increased yelping of eastern coyotes hasn’t caught your attention, you may not be aware that this is the peak of their breeding season. Female coyotes come into estrus once a year, for a period of about 10 days. For the past two or three months, working up to this, male and female coyotes have been increasing their scent marking. Occasionally you can find where a female has marked with urine, leaving behind a spot of blood (see photograph). Eventually she attracts one or more sexually active males, and mating ensues. Something I’ve never witnessed, but would love to, is the howling duet of a pair of coyotes prior to mating.
One night this week I became aware of a series of whistled “toots,” all the same pitch, coming from the adjacent woods. This far-reaching, distinctive call comes from a surprisingly small owl, the Northern Saw-whet — one of our most common owls, whose common name comes from the “skiew” call that is made when it is alarmed. This sound has a resemblance to the whetting of a saw. Although a Saw-whet only weighs about as much as a robin, you would never know it from the volume and carrying power (over 300 yards) of its call. Typically the male calls only during the mating season, in an attempt to attract a female with whom it will mate. The female then selects the nesting cavity, typically a Northern Flicker or Pileated Woodpecker hole, usually in March or April. This pint-sized raptor (weighing less than 3 ounces, and measuring 8 inches in length) feeds mainly on deer mice. Unlike most owls, it does not swallow the mouse whole, but rather tears it in half, leaving the second half for another meal.
Every track you see in this photograph was made by a red fox. Coming from every direction, they all lead to the tree stump. This stump is to foxes what our general stores, post offices and libraries are to us – a place to catch up on all the local news. Red foxes have these “bulletin boards” scattered throughout their territories. By marking a stump, they convey information such as their age, sex, availability, and much more to every other fox that passes by. Foxes will revisit these posts regularly in order to refresh their scent and update the information they’ve left. They also mark the boundaries of their territory to keep other foxes out. To save themselves unnecessary hunting, they mark spots where they have previously searched for prey or cached prey and eaten it, as a signal not to bother to investigate that area. During mating season, which we are in the height of, the fox also uses a scent from a gland on its tail to mark objects. At this time of year the combination of fox urine and glandular secretions create a skunk-like fragrance discernible by the human nose.
Red foxes (and other animals) communicate in a number of ways, one of which is to scent mark with urine. These “sign posts,” along with scat, advertise the fox’s presence, its dominance and sexual status to all other red foxes that pass by. In addition, foxes mark their cached prey to indicate whether any food remains to be eaten. Foxes leave scent marks along the boundary of their territory, as well as within it. Often you will find both urine and scat placed strategically on elevated objects, such as rocks, stumps and vegetation emerging from snow as well as at the intersection of two trails. Both male and female foxes leave scent marks. Researchers have found that when foxes are looking for food, they mark up to 70 times an hour! When just traveling and not hunting, they do not mark as frequently. During their breeding season, which peaks in February, male fox urine takes on a strong skunk-like odor. Only during the past week have I begun to notice this scent where foxes have marked.