ARBORETUM NEWS (NATURALISTSNOTES)

About Mammals in the Arboretum

SUNDAY, FEBRUARY 19, 2012

Today’s topic was mammals. My quick count revealed thirty-eight of them right in front of me on the steps of the Visitor Center. I predicted most of the mammals we would see today were going to be our fellow homo sapiens sapiens. We humans are threatening to most other mammals – they don’t want us to see them. I thought with all this mud, we would at least see plenty of tracks. But, we didn’t. We set out on the Curtis Prairie paths. There were some very frequent and conspicuous signs of a particular mammal that will feed in and around the prairie. This mammal provided the inspiration for naming of one of the ponds within Curtis Prairie – Coyote Pond.

The coyote (Canis latrans) left its mark at intervals of a few hundred yards or so. Coyote feces looks a bit like its canine cousin – the ubiquitous neighborhood dog’s poop. However, a coyote’s is usually a bit thinner and tapered at both ends. And in the winter, coyote feces contain tell tale strands of hair from rabbits, mice or voles, which make up a major portion of its diet in the winter. In the summer, they may be eating a sizable quantity of berries, and berry seeds can be prominent in their scat at this time of year. Not all of us had the intention of taking a scat tour – but the frequency and prominence of this coyote communication was not to be ignored – especially since most of it was smack dab in the middle of the path. Was this intentional? I said yes. And, what is the message? Was any intended communication directed at us? These questions get more complicated.

Those of you who have cross-species communication abilities (you know who you are) may want to discuss this with your dog (and let me know what they say). It’s just this cute relic of evolutionary instinctual territory marking – right?
Scent marking does seem to be an instinctual, evolved form of communication – at least among canines and many other species. Although, the feces of fellow mammals like coyotes are readily seen by visually orientated species like us, the messages are primarily contained in the scent rather than in its visual effect. I’m told that unlike dog scat, coyote scat has a mellow, musky odor. Don’t worry – this is not part of the tour. Musky? Hmm – sounds like something Revlon might mix up for us.

Canines, like lots of other mammals communicate and live in a world that simply is not available to us. We can observe and do some testing and hypothesis – but it is difficult to fully understand what a world is like for creatures who have senses of smell hundreds of times of magnitude more sensitive than our own. It’s a challenge – we are left to use our powers or reason and imagination to attempt to heighten our awareness and perception of their sensory world.

Through various types of testing researchers believe that coyotes can receive and send information to each other about gender, dominance, and breeding status through the scents in their urine and feces. And they will often choose to scent a prominent surface – such as urinating on a tree trunk, or pooping in the middle of the trail. Coyotes have been observed to communicate through scratching the soil and also adding urine to the spot where they scratched the soil. They may also add urine to spots where they left their scat. Statistically, the dominant or mating male does the majority of the scent messaging. Much of this messaging seems to be territorial. And, researchers have observed that coyotes do use the human landscape – our roads, footpaths, farm field and garden edges, etc. as territory markers. Although, it is likely the scent marking is not directed at us, the placement in open areas increases our likelihood of noticing these markers.

To further complicate our deciphering of these messages, we may feel like we are getting a handle on where and how big a coyote territory is – and then it may change depending on who is the dominant male, or changes in the type and concentration of food sources during seasonal or yearly cycles. Territory lines may be drawn closer and defended and marked with greater vigilance for these next few months, as the activities of breeding season are about to begin. Which opens the possibility that the scent marking this time of year may contain communication between breeding males and females. So, could the scent marking at this time of year, or for other times of the year as well, contain more than a single message, or come from more than one individual? Stay tuned – and watch your step!

Although Wisconsin, like most states, permits hunting of coyotes – there is not a widespread thirst to obliterate the coyote population as there was several generations ago. Being resourceful (Wile E coyotes) – they deal with adversities of a human dominated world – us, our vehicles, our flattened landscapes of farm fields, parking lots, city streets, etc., while rejoicing in the attraction of our supplemental food source of garbage cans and alleys, and sheds, etc. that provide shelter, warmth and food for coyote treats such as rats, mice, and other small creatures. Even if we resist the anthropomorphic label of optimist, we can surely proclaim the coyote as an opportunist extraordinaire. Populating the desert west before Europeans came to this continent and then being almost exterminated as the West was won and they became a threat to farm animals, the Coyote has far surpassed its previous range and population. They now range throughout the U.S. north into Canada and south as far as Costa Rica. In addition to their toleration of us and our abilities to quickly and dramatically alter landscapes, eating a wide variety of foods such as small mammals, eggs, fruit, berries, nuts, rodents, fish, carrion, insects, grains, and various types of vegetation is an adaptive strategy used by the coyote and other creatures we call “generalists.”

In today’s world, tolerating humans and their habitats and being a generalist is a crucial aspect in many species’ survival. If you have been seeing hawks around Madison, chances are it was a red-tailed hawk (Buteo jamaicensis). It’s a fairly large bird, about 19 inches tall, with a wingspan of over four feet. It has a curved, sharp bill and rough yellow skinned legs and feet, ending in dark, curved and substantially sharp claws. Looking up at a red-tailed hawk in flight, its feathers near the shoulders and neck are usually dark grey, changing over to a white and then tipped with dark grey at the edges. The adults will have a distinctive fan of brick red tail feathers. Soaring straight at us about 40 feet overhead, most of our group noticed this familiar neighborhood resident.

Was it a male or a female? Females are larger than the males – usually about 25-30% larger. But to us humans, was this a large male or a small female? Although I believe I have seen the same hawk for a few seasons in and around the Visitor Center at the Arboretum, and another one around an old field by my house, and a couple hawks that hunt daily along Stoughton Road – I still don’t know them well enough to make a good guess at sizing up each one as a male or female. Juveniles will not have the distinctive brick red tail that this one over the prairie had. However, it is not likely that many juveniles are around now. Like the coyote, this is the beginning of mating season for the red-tailed hawk, so even the youngest hawks are already ten or eleven months old – pretty much an adult the red-tailed’s average lifespan of 12-16 years. As these longer and warmer days are stimulating hormonal changes, we may observe more territorial and social behaviors such as soaring, chasing, and mates flying together which may intensify during mating season.

So, it’s a good possibility that this low, straight, stiff flight along the edge of the prairie that we saw today was a message to other hawks or other birds of prey, like owls such as: me and the Mrs. (or maybe the Mr.) are settin’ to build a nest near here and we are claiming this area for all the food we will need – for ourselves and our three chicks. I haven’t seen the coyotes watching the hawks, and this message will not be received or perceived by our resident coyotes. I wonder if the hawks would like to send the coyotes a message. The coyotes are constantly hunting one of the hawk’s major food sources – small mammals such as mice, moles, and voles, which can make up to 80% of the hawk’s diet. If hawks could garden, I imagine they would be planting lots of early bearing berry bushes and encouraging baby bunny production to minimize as many coyote rodent buffets as they could.

Is it possible that two predators whose food sources overlap will affect each other’s success? It is possible – and population cycles are an important area of research. However, in places like the Arboretum where populations of predators like hawks and coyotes are not very large, and where they do have other options as far as food sources and expanding or shifting territories – the rise and fall of their populations as well as populations of their prey, like voles and mice, seem to be more dependent on how available and abundant the total of all preferred food source are for each species. So, a great mouse-hunting season for the coyote may not adversely effect the population of hawks.

This is not to say that all is equal and that populations of animals are not affecting each other. Unlike our backyards, you don’t see many bunnies in the Arboretum. Rabbits are on the large and varied bill of fare for coyotes. However, many of the rabbits may make a wise choice not to venture into their predators’ territories in the Arboretum. Research indicates that rabbits will avoid an area that known predators inhabit – and they seem to be able to smell and recognize coyote scent marks. Another creature that smells coyote scent and avoids the area are various species of fox. Likewise, in areas where wolves are present, the coyote will recognize their scent marking and shift their territory away from the wolves’ territory.

The other mammal I don’t see as much of in the Arboretum as I see in the city is the grey squirrel. Does the larger population of predators such as the coyote and the hawks and owls keep the squirrels out? Surely, not entirely. In fact, we saw a red-tailed hawk in a tree downing the last bits of squirrel lunchmeat. And, even though they may not seem as noticeable and abundant – we do hear and see squirrels frequently in the Arboretum. Usually when you hear something that sounds like a deer or a person running through the leaf litter, it is a squirrel. Perhaps the squirrels that live longest in the Arboretum have learned to stay away from the open road and the paths and mowed areas. I see them mostly in areas with more shrubs and trees. Perhaps to stay out of sight and make it more difficult for the coyote pounce or the quick aerial hawk ambush from its perch? When we got into a shrubby tree filled area today, we heard the frantic pattering of sharp squirrel claws scampering up and down and over against the crisp shattering pieces of tree bark. Again, humans are challenged to interpret this behavior. Young ones engaged in this behavior may be releasing energy, or experimenting with dominance behaviors. It seemed that the number of squirrels involved – hard to say – maybe about eight of them – could have been a bunch of males chasing a female. Researchers hypothesize that this may be a “fitness test” in choosing a strong mate. The squirrels’ mating season is a bit later than hawks and coyotes – early summer. Still, could some of this pre-mating behavior be going on now? We not be able to understand all that’s going in, but it’s always fascinating to watch and think about how we and our fellow mammals and other creatures communicate and greet the seasons.

Paul Borowsky
Arboretum Naturalist

Located between Lake Wingra and the West Beltline Highway at 1207 Seminole Highway, the University of Wisconsin-Madison Arboretum features the restored prairies, forests and wetlands of pre-settlement Wisconsin. This 1,260-acre arboretum also houses flowering trees, shrubs and a world-famous lilac collection. Educational tours for groups and the general public, science and nature-based classes for all ages and abilities, and a wide variety of volunteer opportunities for groups, families and individuals are available.