Established wildlife populations generally reach a fluctuating balance around the capacity of the habitat to support them. The size of populations depend largely on birthrate versus mortality. Urban deer currently have a high birthrate and low mortality. The population is increasing. Urban habitat seems not yet at capacity. Without management intervention, factors will ultimately temper increases in the number of deer. What will those factors be? Will those factors be planned management factors, or factors not of our making? Will the deer density be tolerable at that balance? Without active deer management it seems that is not likely.
Having retired from a life’s career as a government wildlife biologist I foresee managing urban deer over the long term being technically difficult, and fraught with political consequences. As with feral rabbits, deer stir emotions of parental protection within many people. Other people, frustrated with deer, want them killed. Here I will proffer a couple options that might be considered as components in an urban deer management strategy.
Backgrounder:
Urbanites are in escalating conflict with deer. That conflict was earlier experienced by apple producers. Some decades ago “old fashioned” trees, largely immune to deer damage, were being replaced with high density plantings of short, spindly apple trees. Fabulous for deer – terrible for apple producers; for deer abundant high quality food and few predators; for orchardists de-barking damage of bucks rubbing antlers, and in particular browsing that could damage the entire leaf canopies of these small trees.
An experimental deer hunting season localized within one community failed to help. Indeed, it seemed to exacerbate the conflict. Excluded by worried private landowners, hunters were forced into adjacent Crown highlands. The consequence: ever-more deer migrated from those Crown lands down into orchards and urban areas seeking safe sanctuary. Hunting in Crown land areas is not likely to be adequately effective in reducing deer populations in adjacent urban areas.
Some orchardists were given permits to kill marauding deer. However, shooting at night the high risk of stray bullets injuring people largely fettered that “cull” option.
Innovative deer repellents such as soap, hair clippings, predator feces (lion dung collected from a local zoo), ultimately proved insufficiently effective. Commercial repellents – odor repellants or taste repellents – were moderately effective in winter. Effectiveness diminished in summer when new leaf growth became vulnerable as it pushed through the protective repellent barrier, and, when repellant potency was diluted by rainfall or irrigation. Further, if alternative food was not available, deer seemed “to hold their noses” and eat regardless of repellants. Repellents work best when there are lots of other food choices for deer to select.
High tensile smooth wire fencing, and electric fencing also proved insufficiently effective. Ultimately, an economic analysis unequivocally showed solid barrier page wire fencing to exclude deer was the most cost-effective solution to minimize deer damage in high value fruit crops.
Urbanites have unintentionally created un-naturally productive habitat for many adaptable wildlife species – of which deer are merely one. Food is abundant, and mortalities are low. Ultimately, would urbanites tolerate deer exclosure fencing throughout their community? Many frustrated residents are resorting to that resolution. Although likely effective in especially vulnerable areas, excessive exclosure fencing may not be generally acceptable. Some folks liken such a fencing scenario to living in a POW camp.
Further, urban deer are becoming familiar with man-made structures, sometimes walking casually onto patios, up staircases, and even into homes. I think more the behavior of coyotes than deer as I watch a doe with two fawns intently digging in soft soil underneath a page wire exclosure fence!
Having taught her fawns the trick, each new generation of urban deer will become ever-more adept at negotiating man-made structures. In urban deer populations there may be an ever-
developed “culture” of living with people, making these urban deer ever-less able to fend for themselves in “the wilds” out of the city.
So, what can people do? To bring these deer populations into a tolerable balance with their urban habitat how can we moderate birth rates, and increase mortality?
A testament to the quality of the diet available in their urban habitat, many female deer are producing twin fawns. In “the wild” food scarcity reduces birth rates. Can we reduce available food hence reducing the birth rate of urban deer by renovating our decorative landscapes; planting only varieties that deer do not like to eat? It seems the palate of urban deer is in flux. As the menu changes deer seem to be eating plants previously thought unpalatable. Plants deemed unpalatable today, may be great deer fodder tomorrow.
Further, it is unlikely people will abandon perennial favorite foods for deer: vegetable gardens, fruit trees, nut trees, flower gardens, cedar hedges as well as other favored shrubs. Deer also enjoy raiding bird feeders.
Of course, people should be discouraged from intentionally feeding deer.
Added to the list of un-natural urban enhancements of deer habitat is our winter maintenance of roads. Compared to backcountry areas, in urban areas roads are not only more abundant but also more rigorously salted due to safety of high traffic volumes. Deer foods in urban neighborhoods has extra potassium. Metabolically potassium must be balanced with sodium. Balancing extra potassium versus sodium could be a contributing reason deer lick roadside salt accretions when succulent vegetation is available. Dietary salt is not likely a limiting factor for urban deer.
To conserve water deer compress their feces into pellets. For example, deer need less water than cattle. Cattle do not pelletize their feces. And yet, water seems to be more readily available in urban areas compared to semi-arid back country habitats. Supplemented by sources such as irrigation overrun, decorative water features, and storm water catchment basins, deer seem to be finding adequate water in the city. Water is not likely a limiting factor for urban deer.
As an aside, here I would like to put in a plug for xeriscaping. Renovating our decorative landscaping to native plants, shrubs and trees would not only reduce irrigation water use, but also be somewhat more ‘natural’ for deer.
As well as changing their dietary habits, urban deer seem to be changing their activity patterns.
Relieved of the threat of predation they are becoming unafraid of people, and, more nocturnal. Urban deer stay up all night. A cull of deer using gun or archery hunters could not access the problem deer within neighborhoods of dense housing without high risks to public safety – especially when light is low.
Similarly, darting deer with immobilizing drugs is not likely to be effective. Darts can cause significant injury to the deer, as well as making the meat unsuitable for human consumption. Worst of all is the prospect of the shooter missing a shot and loosing a drug-loaded dart subsequently picked up by a child and accidentally self-injected. Darting could not access the problem deer within neighborhoods
of dense housing without substantive risks to public safety.
Individual deer traps could safely capture a few deer but are unlikely to be adequately effective over time as deer become ever-more “trap-wary.”
Drop-net traps have been used relatively safely to capture many bighorn sheep at one time. However, food would have to be used to bait urban deer under a net, increasing rather than decreasing the population’s food supply, thus increasing the birth rate of ‘escapees’. Further, baiting to concentrate deer under a net would increase damage to adjacent neighbors.
In the wild, predators remove deer. A principal predator of deer is cougars. A few cougars in urban neighborhoods would likely reduce deer numbers. With inherent risks to public safety would people tolerate cougars in urban areas, or perhaps even less-effective deer predators such as bears and coyotes? Probably not.
Epizootic diseases are wildlife’s equivalent to epidemic diseases in people. There are a few wildlife diseases that might remove large numbers in the urban deer population, leaving carcasses scattered throughout neighborhoods. Some years ago the white-tailed deer population of south-central B.C. suffered an outbreak of EHD, a hemorrhagic virus that kills dramatically and very quickly indeed.
Many deer carcasses littered the landscape. Other species of wildlife were largely unaffected by the virus but the deer population was decimated. However, for management of urban deer intentional infection with disease agents is not ethical.
Some would say the best long-term resolution of urban deer conflicts is to enhance backcountry habitats to provide a better place for deer to live, perhaps imagining if those habitats were improved deer would move out of the city into the country. While in principal enhancement of natural habitats is good for the environment, based on the attractions urban habitats, and, an apparently growing ‘culture’ of urban deer familiarity of with people, I am ever-more discouraged that enhancement of non-urban habitats can out-compete the attractions of our urban habitats. In the city, there are just too many good things for deer, even with people’s best efforts to make it less so.
Part two to be continued next week
- Bob Lincoln