Via Invasive Species Weblog, a story from the Milwaukee Journal Sentinel that the Wisconsin DNR will allow citizens in three southern counties in that state to “adopt” wild Mute Swans and spare them from approved lethal control measures, provided they pay to have them sterilized. [Holds head in hands and groans.]
I’ve previously written about the problem with Mute Swans, which are charismatic non-native invasive species. The state of Wisconsin implemented a successful Mute Swan control policy in 1997, the goal of which was to eliminate most of the state’s swans, especially because they were interfering with efforts to establish native Trumpeter Swans.
soft-headed soft-hearted citizens raised a stink. A revision of the plan was approved in 2002: remove all free-flying wild Mute Swans except in two townships in Racine Co., because residents objected. Now, 86-88% of the remaining swans in Wisconsin are in the three southeastern county region which includes Racine Co.
In December, there was a recommendation (pdf) made to the WI Natural Resource Board to continue the 2002 policy. According to the Journal Sentinel article, because more citizens objected it was instead decided to spare the swans in all three counties (versus just two townships) , as long as the birds are sterilized at citizen expense.
I see a number of problems with this “solution.”
1) Is subjecting swans to pursuit, capture, restraint, anesthesia, and surgery really a humane alternative? Chemical contraceptives are not commonly used on waterfowl, and those not involving capture and direct administration are not species-specific, with the risk of ingestion by other types of birds and animals. Since the article mentions neutering by a vet, the option proposed must be surgical sterilization.
Surgical sterilization was attempted in Michigan, and was unsuccessful; all birds died from complications or infection. Swans do poorly under general anesthesia. A USFWS report on control of feral Mallards also concluded that capture and surgical sterilization had a “high risk of fatal outcome” especially for hens. You can read more about these methods in this Maryland Mute Swan Task Force report.
However, if these citizens care so little about what’s good for the swans that they hand feed them white bread, then perhaps subjecting the birds to all that stress won’t be a deterrent.
2) Allowing some Mute Swans a reprieve allows them to continue to do environmental damage.
a) If a Mute Swan is sterilized and released, it will continue to eat up to eight pounds of vegetation daily for the rest of its natural life, which is up to 25 years in the wild. Ironically, one group of citizens that prompted the new spare-the-swan policy are the residents of Upper and Lower Phantom Lakes in Waukesha Co. The lakes have designated “sensitive areas” in which the aquatic vegetation is critical or unique fish and wildlife habitat. One of the most important native aquatic plant species in the lakes is Vallisneria, or wild celery. This keystone species is very vulnerable to over-exploitation by Mute Swans.
So residents are trying to preserve native aquatic plants species, which coincidentally began to decline around the time Mute Swans began to inhabit the lakes. They are fighting to preserve a non-native bird that is likely to be contributing to the decline of native species which they are also fighting to preserve. By the way, part of the effort to preserve the aquatic habitats in Upper and Lower Phantom involves an aggressive nuisance plant management program. Yet the rationale of some in opposition to the Mute Swan elimination policy (or any non-native species policy) was voiced in a public hearing: that “this country was founded with open arms for anyone as a person to come here and [that] also applied to animals” (hearing minutes in pdf). But not plants, apparently, as non-native species are subject to chemical and mechanical controls.
b) Sterilization does not prevent nesting and consequent displacement of or aggression towards native species in the swans’ territory, including endangered Trumpeter Swans.
3) Is sterilization even an effective method of population control? Very little information. At least with Canada Geese, vasectomy can alter the male’s behavior (pdf), with the male allowing the female to mate with another male. One study of sterilized Canada Geese resulted in 12% of eggs still being fertile.
There is plenty of science behind the decision to remove Mute Swans from ecosystems. There is no science, only sentiment, behind the idea to “save” them. I think the swan adoption experiment, slated to run for a year, was merely a placating measure and that relatively few swans will “adopted.” It staggers me, however, that science cannot prevail in cases like these. Instead, wildlife agencies are tied up in hearings and court proceedings in every jurisdiction this comes up. It’s completely ridiculous.
A reprint of a Ted Williams Audubon article on Mute Swans appears on his blog.