Alternatives to Killing Geese (and other living things).
Barry Kent MacKay | Director
Ever since Animal Alliance of Canada began, we have fought to protect Canada Geese. Canada Geese are only one of seven native goose species that has learned to trust and live comfortably among us. But it is a trust too often betrayed. The urge we continually encounter, the default response, is to do what humans do so well: kill. Killing is often presented as the only effective method of dealing with whatever concerns, real or imagined, people have about these birds. With this first article I hope to show what we have shown so many times – often with significant success – and that no, we don’t actually have to kill them. Sometimes doing so just makes the concerns all that much worse.
Part 1 of 3: Population concerns
The Capital Regional District (CRD), made up of 13 member municipalities from southern Vancouver Island and the Gulf Islands. As you may know, the Board of the CRD, met on Wednesday and approved a Canada Goose Management Strategy, which will include a cull. This despite not having done their due diligence on non-lethal methods, including habitat modification. Our West Coast campaigner, Jordan Reichert, was at the meeting to present our concerns. “It’s incredibly frustrating,” he said.
“I did not know,” said one correspondent, a donor, “that there were options to what we were presented.” She referred to a brief and poorly promoted, thus little known, opportunity in B.C. to comment on the plan to “control” Canada Geese. Implied was that what was being offered by the CRD was both the best, and the only, range of options. Not only are there non-lethal solutions to “problems” created by common species, but for reasons I’ll explain, they usually work better.
When numbers of a common species are reduced through culling, it often results in the surviving individuals having increased survival rates. Increased survival rates could also lead to increased productivity, a phenomenon commonly called, “compensatory mortality” or the “population rebound” effect. A reduction in numbers can result in less competition among survivors for resources, such as food and nesting sites. This can mean that more individuals stay alive, and reproduce, resulting in as many or more individuals than before.
Let’s do a bit of math:
A Canada Goose can lay from two to nine eggs. It takes one to four years, usually three, for a gosling to reach sexual maturity. We start out with two parents; if five eggs are laid each of three years, and all survive, by the time the first cohort of young have reached sexual maturity, there are a total of seventeen birds. Of those seventeen birds, seven (the two original parents plus the first group of their five young) are ready to start over – that is, three pairs, plus a spare individual. They will, if this success rate continues, produce on average a total of fifteen birds, with another generation closing in on breeding age. This, of course, equals “exponential” growth. Canada Geese can live five to twenty years.
But of course, none of that ever happens.
What Happens in the Real World
Goslings and younger geese experience high mortality compared to young and middle-aged adults. Averaged out over time the number of surviving geese is “balanced” by those lost to mortality caused by predation, accident, disease and starvation. This is often called the “balance” of nature, a misleading term as it suggests a steady-state, identifiable point of equilibrium. Such a “point” is forever changing. When the number of individuals of a species – such as the Canada Goose – is equal to what their habitat can support, we say that “carrying capacity” has been reached.
But carrying capacity, or equilibrium, is also not a fixed point; there is no single marker or indicator telling us when it has been reached or exceeded. It is more accurate to realize that the “right” number of organisms is what the habitat is supporting. Starvation, non-breeding adults and occupancy of sub-optimal habitat may indicate especially large populations. Disease and/or starvation may indeed result from more animals than there is food (or other resource) to keep them healthy. But even by that standard, the population of geese the donor was referencing was healthy and increasing. Thus, speaking in the language favoured by wildlife managers and politicians, “carrying capacity” had not been reached. Obviously it would not be reached by reducing goose numbers still more! The math shows that one would have to mass slaughter the geese to get back to where there were not “too many”, a concept that has no science-based meaning in ecology.
The concept of “social carrying capacity” in wildlife management circles
Social carrying capacity is the number of organisms that can share our environment without triggering complaints from voters. Complaints then motivate politicians to “do something”. Social carrying capacity will vary through different parts of the community, with the complainers the “squeaky wheels” who get the attention.
Lethal culling can reduce goose numbers to whatever is socially/economically acceptable, until the population builds back up, but only if the slaughter is huge. That solution is not only disagreeable to most folks but can violate core mandates of wildlife management agencies. Instead, they may try to appease all “factions” and interest groups by allowing a range of responses to the “problem” – something for everyone – thereby perpetuating the problem into the future.
What has been successful in so many instances is “habitat modification” in conjunction with education, and the implementation of various “best practices” backed by at least a degree of enforcement, all of it based on knowledge of Canada Goose behavior and requirements at various stages of the life cycle.
