White-tailed Deer feeding sign at Kinghurst
Recently, at a TCNA “tracker tuesday” call, there was a challenge proposed: on your next tracking outing, practice following the deer or the rabbits and see if you can find 10 plants which they fed on. For me in my area, the deer would be White-tailed Deer (Odocoileus virginianus) and the rabbits would be Eastern Cottontails (Sylvilagus floridanus). While I have been observing the Cottontails loosely at work with my students, for this tracking outing with the Earth Tracks Wildlife Tracking Apprenticeship, we focused on the White-tails.
Winter food finding in Southern Ontario is tough for all species. Not only is there a lot of snow on the ground, many of the common forbs which the Deer consume are long dead and the remaining and accessible plants are mostly tougher woodier species which tend to be harder on the teeth and harder to digest. In addition to these impediments White-tailed Deer prefer a mixed bag of food sources. They tend to seek out a variety of mixed forage. While occupying smaller “yards” or Winter territories the White-tails often have less diversity of choice. While their Spring, Summer, and Fall diets are of a more cosmopolitan variety, in Winter they are forced to live off less.
It’s important to consider not only what the deer are eating, but also how. Let’s remember the basics. White-tailed Deer bite off the ends of twigs with their incisors, the teeth at the very front of the mouth. We may think of our own incisors at the top and bottom in the front of our mouths, but when it comes to the Deer they only have incisors on the bottom mandibles. This is also true for a few other species as well, such as everyone else in the family Cervidae (including deer, Moose, Caribou, Reindeer), members of the families Giraffidae (Giraffes, etc), and the family Bovidae (Cows, goats, sheep, etc). All members of these families have no incisors in the cranium. Instead, when they bite those twig ends off they rip them off by grasping the twig end between their lower incisors and the hard palate above. Some other species, such as members of the Rodentia and Lagomorpha orders, cleanly slice twig ends off, but for these no-upper-incisor-having species, it’s often a ragged rough hewn rip. See if you can see this in the photos below.
In “Deer (The Wildlife Series, Book 3)” (Stackpole Books, 1995), Dietland Muller-Schwarze wrote that Deer, like other ungulates, have quite a lot of circumvallate papillae (one type of many bumpy structures on the tongue that gives it the rough texture). In Humans (Homo sapiens), we have between 8-12 of these large structures near the back of our tongue and each structure holds about 100 taste buds. These taste buds on the circumvallate papillae are especially sensitive to bitter tastes. Muller-Schwarze writes about how Deer will commonly spit out bitter forage when they come across it, but for me, this begs the question of how bitter is too bitter for a Deer? Some of the plants described above and below can be pretty bitter tasting to me but I am curious about the time of year when bitterness is most expressed in a plant? I think of bitter annuals in early Spring like some of the Mints (Lamiaceae) and Mustards (Brassicaceae), how often to the Deer munch on these? Perhaps we’ll need to keep an eye out in the Spring to find out.
Lucky for the Deer at Kinghurst, there is a variety of fine forage for them in the Winter. Here I will share some of the variety of plants which we observed feeding sign on, listed in the order in which we came across them. I would love to trail the deer in other areas in Southern Ontario and see what they forage on there. Next time..
1) Alternate-leaved Dogwood (Cornus alternifolia)
The Alternate-leaved Dogwood is also known as Green Osier and Pagoda Dogwood. I think Pergola would be a better name as a pagoda is multistoried and closed on the sides, while a pergola is single storied, and open, more closely resembling the growth form of this outlier in the Cornus genera. I write outlier because the Alternate-leaved Dogwood is just that, alternately leaved and branched, while the rest of the Cornus are opposite branched or whorled. White-tailed Deer tend to consume both the leaves and the twigs.
C. alternifolia is plentiful at Kinghurst. They tend to grow as an understory shrub in open woods, ravine slopes and hillsides, in forests with mature canopy species such as Sugar Maple, Eastern Hemlock (Tsuga canadensis), and Yellow Birch (Betula alleghaniensis). There are the places where the White-tail tend to hang out.
2) White Ash (Fraxinus americana)
Common species in the upland forested landscape which I tend to see coming up quickly in areas where other coniferous trees have come down, leaving a gap in the canopy. Most of the larger White Ash and Black Ash (Fraxinus nigra) we found were riddled with Emerald Ash Borer (Agrilus planipennis or EAB) sign and epicormic shoots, but the younger ones the deer were hitting, not so much. We did find one massive old White Ash with a Winter Porcupine (Erethizon dorsatum) den in the base, with the Porcupine huddled up inside. I did not see any sign of EAB on this big one and wonder if they are resistant somehow? If this individual tree is resistant somehow, I hope they are a pistilate or seed flower bearing individual (White Ash trees are either pollen flower bearers or seed flower bearers) and survive to spread viable seed with that same possible EAB resistance. We noticed lots of feeding sign adjacent to the den, but this was Porky sign with 45°ish cuts at the end rather than the ragged cuts the deer tended to leave behind.
3) Eastern White Cedar (Thuja occidentalis)
Eastern White Cedar is the one of the most important food plant in the Northern woods; one of the only green plants in the NorthEast which can sustain deer in the critical part of Winter. Aside from being an essential food source, White Cedar also provides good thermal cover in the Winter months similar to Eastern Hemlock (Tsuga canadensis). The White Cedar grow in tight groves helping keep the snow cover below shallower than surrounding open forests.
As White-tailed Deer move through White Cedar groves they tend to feed on all the green leaves from the lower branches within reach, often creating visible, generally uniform horizontal browse lines. These browse lines are a clear indicator of White-tailed Deer population in a given area.
4) Black Locust (Robinia pseudoacacia)
Black Locust is a tree that I have read described as a non-native invasive species which chokes out local tree populations. I have seen this native to the faraway distant (note the sarcasm) mountain tops of Pennsylvania to be an early colonizer of meadows and preventing erosion by stabilizing soil with an extensive root system. The bees love the beautiful and tasty flowers and it seems the White-tailed Deer appreciate the young shoots for Winter browse. The Black Locust was once planted for the valuable wood and also as a beautiful ornamental with their amazing dangling, pungent flowers. While the thorns may be irritating, they have developed on the tree to prevent too much herbivory by from the Deer while still giving something in the way of a good food. If only we could all learn good boundary making like this plant.
I noticed many of the individual Black Locust trees growing at Kinghurst were growing in open canopied clearings along the edge of the pine plantations, and this makes sense as they are intolerant of shade. I would imagine as more mature trees come down in that forest, more Black Locust will be coming up. They can do this quite easily, and they don’t need seeds. The Black Locust commonly spreads by sending up “ramets” or shoots from underground runners. If the Deer did consume a new shoot all the way to the soil, then the root would just send up another one.
5) White Pine (Pinus strobus)
For all it’s ubiquity, I don’t believe I have ever noticed White Pine being browsed by the Deer until this occurrence. I know this is a common occurrence detailed in the literature I have read, but I had not seen it before. I appreciate this assignment as I am now looking at this pretty common species in new light and noticing something that has likely been there forever, but is new to me. The White Pines I encounter also seem to be very large and in mature forests where the White-tails cannot reach the lowest branches but I am going to have to pay a lot more attention now just in case.
6) Common Blackberry (Rubus allegheniensis)
Similar to the Black Locust above, the Blackberry has a perennial root which sends up shoots. Instead of ramets, they are called canes which have a two year life span. Also similar to the Locust, Blackberry is intolerant of shade, I guess I am seeing a pattern. The Locust, and the Blackberry were both growing at the edge of the Pine plantation. This lets me know that the area is likely pretty sunny and that the Deer are moving through there.
White tailed Deer population thrive in edge spaces. The edges of a White Pine plantation, the edges of a field, the edges where suburban homes meet the green corridor protecting the creek. These are also prime places for the disturbance adapted plants such as Blackberry and the Locust and a host of other forbs. These help create a rich and varied diet for the Deer.
7) Red-osier Dogwood (Cornus sericea)
The Red-osier has a broad range, covering the boreal and temperate forest regions across the continent, so of course the White-tailed Deer, with a similarly broad range will encounter this shrub. Identified by the red bark on twigs and upper branches, a red which appears to grow redder when the Winter season starts to consider the shift to Spring. Often growing in wetter areas, good to look out for to know where the water might be in a snow covered landscape.
This shrub has taught me a lot over the years. So much so, that I purposely go check out the C. sericea when I am out tracking because it is very likely I will find sign of deer browse. I don’t know if it is the ubiquity of the plant or the blazing red which draw the deer in, but they appear to like this one a lot. I have seen some Red-osiers hit so hard they look as if a bonzai beginner just learned how to use their sheers and got snip happy, stunted and oddly growing, though without a clean cut. This is a good one to look out for on the land when wondering where the deer may be hanging out.
8) Black Cherry (Prunus serotina)
I associate many of the included species with medicinal action in the human body, and I wonder about these same actions with the Deer? I recognize we have different physiologies, but could they work similarly in an ungulate body as they do in a primate body? And if there is similar action medicinally, what about toxins? I have found White-tailed Deer browse on deadly poisonous Water Hemlock (Cicuta maculata) in the past yet did not find a dead Deer beside the plant. Same with Canada Yew (Taxus canadensis); feeding sign, but no dead animal. Do the Deer feed on the foliage of the Black Cherry or just the twigs? The leaves are full of cyanide and could be pretty harmful but perhaps the Deer have more suitable browse in the months when the Cherry leaves are present? I have also read that the twigs have cyanide present, but perhaps not as much as the leaves? Or maybe it just doesn’t bother the Deer at all and they’ll just eat what they want?
9) Sugar Maple (Acer saccharum)
Sugar Maple is a tree I could also get down with munching on. While a little bit bitter from the chlorophyll, the inner cambium still tastes pretty good. Yes, I have tried it. I have also eaten some buds on Sugar Maple in the past and I remember thinking they were palatable. Something I have also learned through the apprenticeship program is to identify Sugar Maples by looking at their the buds at the end of the branches, also called “terminal buds” (which happens to be the name of my nature gang). Sugar Maple terminal buds tend to narrow towards the tips and are more pointed and sharp feeling than, say, a Red Maple (Acer rubrum), which has rounder terminal buds. So the mnemonic “sugar sharp” can help us remember the Sugar Maples, and “red round” for the Red Maples.
10) Wild Grape (Vitis sp.)
A couple of weeks ago during an apprenticeship meet up at Dunby road, we had found feeding sign from White-tailed Deer on some feral Apples (Malus domestica) and some Grape (Vitis sp.) vines. These were very fresh and clear to see. Now fast forward to the outing at Kinghurst, where we struggled to find feeding sign on Grape for quite a while. I was excited when we found it.
I love eating the forked tendrils which grow at the ends of the Grape vines as they are crunchy similar to a Japanese Knotweed (Reynoutria japonica) have a slightly sour and bright flavour. I have eaten them on their own and in salads. I bet the Deer would also go for them in the Spring. But do they eat the leaves as well?
11) Hop Hornbeam (Ostrya viriginiana)
I had never seen feeding sign on Hop Hornbeam from an ungulate until this outing. I have seen individual pouches from the hop-like seed clusters opened by Eastern Chipmunks (Tamias striatus) but never had I seen the browsing on the twigs. Since then though, I have seen more ungulate feeding sign, namely Moose (Alces alces) up in Algonquin Park. I wonder if, like Porcupines (Erethizon dorsatum), Deer have specific browse that they tend to have individual preferences for? Do some Deer like the Hornbeam while most don’t find it palatable? Or is it just a case of my not seeing it before as most of the Hornbeams I notice are older, taller and have little to no lower branches within reach of the Deer to browse on?
12) American Beech (Fagus grandifolia)
American Beech seeds are tasty. I have found them hard to gather as a lot of seed cases turn out empty, and a bit tedious to collect so many tiny Beech “nuts” even when the cases are full. It takes a long time to gather even a few seeds. I remember once gathering about a cup of seeds with friends a few years back and between the three of us it took about an hour. I wonder if the Deer can smell it when the seed cases are full versus when they are empty? As for the twig browse, there was only a bit of browse at Kinghurst, but again, in Algonquin the Moose were hitting it pretty hard in some areas.
and one more bonus conundrum…
13) Digging?
I have seen sign of deer digging through the snow to access ferns and acorns before, but in this case there were no Oaks (Quercus sp.) or acorns around that I know of, and I couldn’t see much in the snowy debris of ferns which had been consumed. We were wondering if the deer were searching out roots of some kind, or perhaps they were feeding on some green shoots of grass, which however rare or unusual, has been observed in the past. Because I cannot determine exactly what the deer were after, I have included this as a bonus find, to be observed further in the future.
To learn more :
The Deer of North America by Leonard Lee Rue III. Lyons Press, 1997.
Trees of the Carolinian Forest by Gerry Waldron. Boston Mills Press, 2003.
Animal Skulls by Mark Elbroch. Stackpole Books, 2006.
Deer (The Wildlife Series, Book 3) edited by Duane Gerlach, Sally Atwater & Judith Schnell. Stackpole Books, 1995.