University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln

3 - Third Eastern Damage Control Conference (1987) Eastern Wildlife Damage Control Conferences

October 1987

URBAN GRAY DAMAGE AND POPULATION MANAGEMENT: A CASE HISTORY

J. Hadidian Center for , National Park Service

D. Manski Aniakchak National Monument and Preserve, National Park Service

V. Flyger University of Maryland, College Park, MD

C. Cox U.S. Soldier's and Airmen's Home

G. Hodge Humane Society of the United States

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Hadidian, J.; Manski, D.; Flyger, V. ; Cox, C.; and Hodge, G., "URBAN GRAY SQUIRREL DAMAGE AND POPULATION MANAGEMENT: A CASE HISTORY" (1987). 3 - Third Eastern Wildlife Damage Control Conference (1987). 19. https://digitalcommons.unl.edu/ewdcc3/19

This Article is brought to you for free and open access by the Eastern Wildlife Damage Control Conferences at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in 3 - Third Eastern Wildlife Damage Control Conference (1987) by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. URBAN GRAY SQUIRREL DAMAGE AND POPULATION MANAGEMENT: A CASE HISTORY

by J. HadidianJ/, D. Man ski 2./, V. Flygeri/, C. Cox1!/, and G. Hodge5/

ABSTRACT Lafayette Park, a 3.0 ecological bases for high hectare national park located squirrel numbers. Action was across the street from the taken through a program of White House in Washington squirrel relocation and D.C., has had a gray squirrel habitat modification to reduce (Sciurus carolinensis) density available den sites. These as high as 50 animals/hectare. programs were coordinated to In recent years this large minimize impact on the population caused significant existing population, and damage to mature trees and continued monitoring has been other vegetation. In keeping used to evaluate efficacy. with the legislative mandate The implications of this to protect and preserve the program for resolving people- historic landscape in wildlife conflicts in urban Lafayette Park, the National environments are discussed. Park Service implemented a squirrel management program INTRODUCTION following an Integrated Pest Although wildlife diversity Management (IPM) approach. The often suffers in urban areas, population was studied and those species which are found monitored to determine the may occur at high population densities (Sc.hinner & Cawley 1974; Goszczynski 1979; Harris I/Center for Urban Ecology, & Rayner 1986). This can lead National Park Service, to undesirable situations, National Capital Region, 1100 such as increased damage to Ohio Drive SW, Washington, the environment, competition D.C. 20242. which excludes desirable S-^Aniakchak National species, or to stress and Monument and Preserve, overcrowding within a given National Park Service, P.O. 7> population. Where wildlife King Salmon, AK 99613- populations come into close I/Animal Sciences contact with humans, public Department, University of health problems can become Maryland, College Park, MD issues as well. 207^2. While these concerns would H/U.S. Soldier's and seem to make it important that Airmen's Home, 1300 North high urban wildlife Capital St. NW, Washington, populations be prevented, D.C. 20317 - competitive and sometimes 5/Humane Society of the contradictory interests can United States, 2100 L St. NW, work to keep this from Washington, D.C. 20037. happening. Traditional

219 wildlife management is often to cause its cancellation. not possible in urban areas. Criticisms were leveled Hunting and trapping are against the NPS for not reasonably viewed as dangerous demonstrating that to humans or domestic pets, were responsible for the and other lethal controls are damage to vegetation, for likely to be inhibited because lacking population data to of public concern for the validate the assumption that welfare of both target and the squirrel population was nontarget species. excessively large, and for Responsibility for wildlife proposing relocation, an may be shared by a variety of undemonstrated management authorities, such as local alternative, as the only humane societies, animal option for squirrel control. control agencies, parks and A subsequent study found recreation departments, and the Lafayette Park gray public health offices, between squirrel population at a far which communication and greater density than reported coordination may be elsewhere (Manski et al. inefficient. As a result, 1981). Intensive provisioning urban governments may limit by the public was implicated their wildlife management as one of the main factors practises to reacting to responsible for this. Also localized crisis situations contributing was the presence and lack long-term planning of a large number of nestboxes for wildlife in either its and tree dens. One result of positive or negative senses. the study was to provide The management of the gray specific recommendations for squirrel (Sciurus managing the population, the carolinensis) population in implementation of which began Lafayette Park, Washington, in 1985. This paper evaluates D.C., reflects many of the these actions in relation to problems and concerns that the Lafayette Park squirrel arise in dealing with urban population ecology and wildlife species. Since the discusses the implications for 1940s squirrels have been other programs aimed at reported to be a nuisance and resolving people-wildlife concern because of damage they conflicts in urban caused to park vegetation. In environments. 1977 squirrel density in the We are grateful to park park was said to have exceeded managers C. O'Hara and A. 31.3 animals/hectare, and Calhoun for their support and squirrels were blamed for over help in implementing the $4,500 damage to annual squirrel management program. and trees. An attempt to Drs. W. Anderson and R. reduce the damage led to the Hammerschlag have provided relocation of squirrels to scientific support and input other areas in the city. This to planing as well as numerous program was criticized by both insights into the special private citizens and animal problems encountered during welfare groups, and adverse the management program. Cyndee media attention was sufficient and Bruce Archer are thanked

220 for coordinating efforts to ten percent occurs as formal place squirrels with flower beds. Nearly thirty rehabilitators. Many species of introduced and volunteers have assisted in native trees and shrubs grow squirrel workups and censuses in the park, with oaks and their help is gratefully predominating. Many of the acknowledged. trees have particular historic and aesthetic value because of STUDY AREA their size, form, and old age. Lafayette Park, a 3 hectare Details concerning the (7.5 acre), formally plantings and layout of the landscaped urban park, is park can be found in Olszewski located across Pennsylvania (1964) and Manski et al. Avenue from the White House in (1981). Washington, D.C. This land, obtained by George Washington MANAGEMENT ACTION in 1791 from an apparently Management of the Lafayette reluctant owner, was intended Park squirrel population to become part of the White commenced in 1985 after House grounds. Thinking this discussions with the feeders might make the president's indicated that over 75 pounds grounds seem too royal, Thomas of peanuts were being Jefferson authorized use of distributed each week. Using the area as a public park. established censusing The earliest definitive techniques (Manski et al. landscaping plan for the Park 1981), monitoring of squirrel is the 1853 plan of Andrew numbers in August indicated Jackson Downing. The most that population levels were recent was approved by commensurate with earlier President Kennedy in 1962 years (Table 1). Since the (Olszewski 1964). situation had not changed, and As part of the National management remained concerned Park system, Lafayette Park about continued damage to park has been managed since 1933 vegetation, a one-time effort with the primary purpose of to reduce the squirrel protecting and preserving the population to a level from historic landscaping themes which other management established by Downing. The practices could be implemented park is listed on the National was planned. The Humane Register of Historic Places Society of the United States and all management activities (HSUS) and the Washington are guided by NPS policies Humane Society (WHS) were relating to cultural resources involved in planning management and the National discussions to resolve Historic Preservation Act. potential conflicts before Lafayette Park is implementation of any actions. surrounded by heavily used Relocation: streets. Approximately half The Manski et al. (1981) of the park is comprised of study had recommended turf; brick walkways make up euthanasia rather than another 34 percent; about relocation as a means of reducing the population, due

221 Table 1 . Lafayette Park Gray Squirrel Census Data 1980-87 * Date Counts Mean # Stnd Date Counts Mean # Stnd Squirre Is Dev Squirrels Dev

1980 1986 Jan 4 63.5 23.0 Jan 8 21 .0 5.8 Mar 7 55.7 18.1 Feb 4 16.5 1.0 Apr 4 68.8 13-5 Mar 8 26.3 5.9 May 4 106.0 4.5 Apr 12 29.4 8.1 Aug 5 92.4 19-9 May 12 37.4 5.8 Sep 2 120.5 3-5 Jun 12 44.8 6.4 1981 Jul 8 31 .8 12.0 Jul 5 150.6 62.5 Aug 12 34.9 9.1 Aug 3 102.7 37.0 Sep 12 42.2 7.8 Oct 4 140.0 32.5 Oct 12 50.3 13.9 Dec 6 122.6 18.3 Nov 12 60.8 4.1 1982 Dec 12 41.8 10.2 Jan 3 88.0 25.4 1987 Mar 3 82.0 7.0 Jan 12 12.7 6.7 May 4 119.8 8.1 __ 17 squ irrels removed -- Jun 3 122.0 17-4 Feb 8 14.9 6.6 Aug 2 115.0 11 .3 Mar 12 16.5 2.5 Oct 4 137.3 3.1 Apr 12 21.8 4.3 1985 May 12 32.3 6.0 Aug 8 102.8 11.1 Jun 12 23-6 3.2 Sep 12 121 .2 23.2 Jul 12 27.7 3.3 Oct 8 104.6 13-8 Aug 12 24.8 10.3 __ 78 animals relocated -- Sep 12 30.7 5.5 Nov 8 63.9 8.1 Oct 12 32.1 3.6 Dec 4 46.8 5.0 Nov 12 30.8 4.1 to the uncertainties aided the decision to surrounding the fate of both relocate squirrels. the relocated squirrels and the The goal of the relocation resident animals in areas to was to remove at least half which squirrels might be moved. of the population. Relocation The actual choice of relocation sites at least two miles as the management option distant were surveyed the reflected the realization that week before the first date public opinion would be chosen to move squirrels. strongly against euthanasia and Thirty-two sites totaling would likely lead to the over 500 hectares of program being interrupted deciduous forest were again. Relocation was planned identified. Since we were to coincide as closely as unable to determine squirrel possible with the period for densities in relocation dispersion among gray squirrels areas, an effort was made to (Flyger & Gates 1983). The select wooded tracts fortuitous occurrence of an dominated by oak and beech, unusually abundant mast crop with close access to sources

222 Table 2. 1985 Squirrel Relocation. Adult males are identified by having descended testis and pigmented scrota. Adult females are identified by having pigmented and enlarged teats. Two squirrels captured and examined were not relocated. ______october~~2TJ Total Total Squirrels Relocated: 4lT IB" Captured Squirrels: Adult Males 11 12 23 Adult Females 11 21 32 Breeding . 6 7 13 Nonbreeding 5 13" 18 Unknown Status 0 1 1 Subadult -Males 8 3 11 Subadult Females 11 3 Total Male 19 15 34 Total Female 22 24 46 of water. The mature Post-relocation Population woodlands chosen met general ChangelT: requirements for good gray With this removal of 78 squirrel habitat (Flyger & squirrels in October 1985, Gates 1983; Williamson 1983; approximately 60 squirrels McPherson & Nilon 1987). remained in Lafayette Park Forty squirrels were moved (Table 1). Between November between 10:30 pm and 4:30 am 1985 and February 1986 this on October 17th and another 38 population declined to fewer on October 24th (Table 2). than 20 animals, a further The squirrels were caught as drop of approximately 75 they slept in nestboxes, percent. Part of this decrease examined after being can be explained by known anesthetized, and held in wire mortality. Dead squirrels mesh transfer cages (52x16x15 began to be observed by park cm). At the release sites maintenance personnel with these cages were propped some regularity beginning in against tree trunks and December 1985 - These early opened, encouraging the deaths went unreported, squirrels to take refuge in however. Seven carcasses were the trees. No more than six eventually submitted to the squirrels were released at any United States Fish and one site, the average being Wildlife Service's National three. The relocated squirrels Wildlife Health Center (NWHC). were distributed so that an Chlorophacinone, the active average of 4.25 hectares of ingredient in a rodenticide good squirrel habitat was used in Lafayette Park to available for each. control Norway (Rattus

223 norvegicus) populations, was All animals showed signs of identified in the stomach fighting and wounding, with contents of two squirrels. obvious skin infections and However, because of the subcutaneous lesions. The presence of blood clots in general diagnosis was these animals' hearts, cause septicemia from infected bite of death could not be wounds due to intraspecific positively attributed to conflict. Streptococcus sp. Chlorophacinone poisoning. and Staphylococcus sp. were Also isolated from a number cultured from all three. of the carcasses submitted was Salmonella typhimurium was the pathogenic bacterium, cultured from the liver and Erysipelothrix rhusiopathia. intestine of one animal. Klebsiella pneumoniae was A fecal sample from the animal isolated from a liver abscess examined by the NZP indicated in one other squirrel. The numerous coccidia and presence of Erysipelothrix had strongloyides . previously not been recorded The number of deaths, for tree squirrels, and was condition of the remaining cause for concern given its squirrels, indications that human pathogenicity. An further mortalities would effort was made subsequently occur, and clear suggestion of to collect and incinerate all stress and overcrowding led to squirrel carcasses found, and agreement between the park to ensure proper handling of managers and humane society these by collectors. Local representatives that a further public health officials were population reduction was notified and closer than usual mandated. On February 14th monitoring of the population seventeen squirrels were taken occurred. at night from nestboxes and Recruitment from two examined under anesthesia: litters and possible four adult males, five adult immigration caused a four fold females (one with week-old increase in the park squirrel young), six subadult females, population by the fall of 1986 and two subadult males. All (Table 1). However, a were in poor condition, with dramatic decline was noted in apparent bite wounds and December 1986 suggesting a numerous suppurating skin process similar to the decline lesions which had left some of the previous winter. animals with large hairless Reports of dying and dead areas. Since it appeared squirrels were again received unlikely that any would at the park; 35 dead squirrels survive removal to natural were collected between areas at that time of year, December 26, 1986 and February these squirrels were placed U, 1987. with professional wildlife Three adult males were rehabilitators. The submitted to NWHC for rehabilitators held the examination, and a fourth was squirrels in outdoor cages for examined by the National the remainder of the winter, Zoological Park's (NZP) Department of Pathology.

224 placing some on antibiotic major feeders continued to therapy, and giving all express concern for the shelter and adequate diets. welfare of the squirrels. One All of the rehabilitated of these feeders, unable to squirrels regained apparent visit the park, hired a street good health and were released person to store and distribute early in the spring as natural peanuts. Only after the foods became available. None second population crash in were returned to the park. No 1987 was a voluntary reduction further deaths of squirrels in feeding achieved, after one remaining in the park were feeder remained in ill health confirmed until a single- and the second had retired and animal was found in April. The no longer wished to make the squirrels remaining in the long journey into . park which had shown skin Between February and April lesions and wounding appeared 1987 the total weekly feeding to recover fully. of peanuts was reduced from 75 Nestbox and Den Tree Removals: to 25 pounds. In April Following the second responsibility for all feeding relocation period in October was assumed by the Park 1985, six of the 18 nestboxes Service. By June the amount in the park were removed. A of peanuts provided had been gradual removal of additional reduced from 25 to ten pounds boxes then occurred, and when per week. The squirrel squirrels gnawed through the population remained fairly wire supports and boxes fell stable through the summer, from trees they were not varying between 25 and 30 replaced. By January 1986 animals (Table 1). there were ten boxes, and by April of that year two more DISCUSSION had come down, to bring the By documenting the total to eight. Between then ecological bases underlying and February 1987 two more the squirrel population removals occurred, leaving the problem in Lafayette Park and six boxes which remained implementing a management through September 1987 • program aimed at long-term Den trees were removed as habitat modification, the park they died, since dead trees managers have been following were perceived as hazards to an Integrated Pest Management people and were inconsistent (IPM) approach to problem with the aesthetics of the solution. IPM was introduced park. Five known den trees in into the National Park Service all were removed following in 1979 as a decision making October 1985: four in August, process with four major 1986 and one in December, components: monitoring, 1986. establishing thresholds, Provisioning; acting, and evaluating Repeated attempts to (Ruggiero 1986). The achieve a reduction in implementation of IPM for supplemental peanut feeding squirrels in Lafayette Park were frustrated as the two . arose because of the

225 management objective of lacking in a broader maintaining the historic understanding of issues that landscaping themes of Andrew pertain to populations. In Jackson Downing. Allowing the Lafayette Park we encountered presence of squirrels at the the quintessential expression extraordinary population of this; individuals who fed densities found in the early squirrels out of concern for 1980s was not an acceptable their well-being management alternative. While inadvertently enhanced the we remain uncertain as to squirrel's vulnerability to exactly how many squirrels the the many environmental, social park can support before and demographic processes unacceptable damage occurs, which regulate population the management objective density. continues to be to seek that Although well intended, we balance where the positive view the effect of large-scale values of having squirrels provisioning on the Lafayette outweighs the damage they Park squirrel population as sometimes do. having been negative. One The central issue in regard major problem with to the Lafayette Park squirrel artificially maintaining the problem has been the role of high squirrel density through the feeders, their actions and provisioning was that other responsibilities, and the important habitat components, influence they have had. such as den sites, became Manski et al. (198 1) limiting. During the winter, established that provisioning this apparently became was an important proximate critical, as many squirrels factor in supporting the high could not secure adequate squirrel population. Before shelter and birthing dens. there could be a lasting Contributing to this was the reduction in the population, high level of maintenance there had to be a significant practiced in the park, which decrease in the amount of food led to the removal of leaf provided by the public to litter that otherwise might squirrels. Despite repeated have been used by squirrels to attempts, a cutback in feeding rebuild nests throughout the was not achieved until well winter. after other management actions Although we employed had been implemented. In relocation as a management effect, a major component of tool, we continue to have deep the proposed management concern for the impacts of program was undermined by a this procedure on both few well meaning but ill- released and, resident advised individuals. squirrels. Research is clearly In a survey of American mandated to determine the many attitudes towards animals, factors and processes which Kellert and Berry (198O) found might influence using urbanites to have great relocation as a management concern and empathy for the action, and the consequences welfare of individuals, but which these actions might have

226 for both humans and wildlife Ecol. 55: 575-591 . alike. Questions still remain Kellert, S.R & Berry, J.K. concerning the Lafayette 1980 Phase III: knowledge squirrel population and its affection, and basic future, and management is now attitudes towards animals and will be for some time an American society. USDI: active concern. Monitoring Fish & Wildlife Service. will continue for changes in the squirrel population that McPherson, E.G. & Nilon, C. may shed some light on the 1987 A habitat suitability population dynamics of the index model for gray squirrels in this urban park. squirrel in an urban ceme- Supplemental feeding by the tary. Land. Jour. 6(1): NPS will be gradually phased 21-30. out, and nestboxes will continue to be removed. When Manski, D.A., VanDruff, L.W., necessary we will use contacts & Flyger, V. 1981 with local rehabilitators to Activities of gray remove diseased or stressed squirrels and people in a squirrels. Finally, a most downtown Washington, D.C. significant component of the park: management implicat- squirrel management program in ions. Trans. 46th N. Amer. Lafayette Park will be Wildl. & Nat. Res. Conf., continued evaluation, as we Pp. 439-454. strive to learn about the many factors which affect Olszweski, G.J. 1964 Lafay- population dynamics in this ette Park. Nat. Cap. Reg. small urban park. Hist. Ser. No. 1. USDI: Nat. Park. Serv. REFERENCES Flyger, V. & Gates, J.E. 1983 Ruggiero, M.A. 1986 The rat- Fox and gray squirrels. In: ional use of pesticides in Chapman, J.A. & Feldhamer, park and recreation areas. G.A. (eds.), Wild Mammals Trends 23(1): 10-14. of North America. Pp. 209- 229- Baltimore: The Johns Schinner, J.R. & Cawley, D.L. Hopkins Press. 1974 The ecology of urban in Cincinnati, Goszczynski, J. 1979 Density Ohio. In: Noyes, J.H. & estimation for an urban Progulske, D.R. (Eds.), population of the field Wildlife in an Urbanizing mouse. Acta Theriol. Environment, Plann. & 24(31): 417-427. Resour. Dev Serv. No. 28, Pp. 125-130 Amherst Mass: Harris, S. & Rayner, J.M.V. Holdsworth. 1986 Urban fox (Vulpes vulpes) population Williamson, R.D. 1983 Identif- estimates and habitat ication of urban habitat requirements in several components which affect British cities. J. Anim. abun- dance. Urb. Ecol. 7:345-356

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