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R E P O R T

Evaluation of Mink - Presence/Absence,Distribution, and Abundance in the

Housatonic River Floodplain

General Electric CompanyPittsfield, Massachusetts

September 2002

BBCBLASLAND, BOUCK & LEE, INCengineers & scientists

Superfund Records Center SITE: G£ -hW^-i B R E A K : 1-1

"-6^07 Coipoiate Environments/ Programs Genera/ Flectnc Company

WDWoodlawnAvenue,Pittsfield, MA 01201Sentpmher 1 8 900?

Susan Svirsky U.S. Environmental Protection Agency c/o Roy F. Weston Inc. 10 Lyman Street Pittsfield, Massachusetts 01201

Re: GE-Pittsfield/Housatonic River Site - Rest of River Report on Mink Field Study

Dear Ms. Svirsky:

Enclosed please find three copies of the following report for your consideration:

• Evaluation of Mink - Presence/Absence, Distribution, and Abundance in the Housatonic River Floodplain, prepared by BBL, Inc. (September 2002).

As with our other studies, we anticipate that EPA will review this study and include the results as part of EPA's Ecological Risk Assessment.

A report on the kingfisher field study will be provided to EPA shortly.

Very truly yours,

Andrew T. Silfer, P.E. GE Project Coordinator

cc: Bryan Olson, EPA* Tim Conway, EPA* Holly Inglis, EPA* Susan Steenstrup, MDEP* Thomas Angus, MDEP* Roderic McLaren, GE Michael T. Carroll, GE Kevin Mooney, GE* James Bieke, Shea & Gardner* Sam Gutter, Sidley Austin Brown & Wood*

* One copy enclosed.

Table of Contents Section 1. Introduction and Background 1

Section 2. Materials and Methods 2

2.1 Study Area 2 2.2 Scent Post Stations 2 2.3 Snow Tracking/Transects 2

Section 3. Results 3

Section 4. Discussion and Summary 5

Section 5. References 7

List of Tables Table 1. Mink Track Observations 8

List of Figures Figure 1. Mink Track Locations 9

BLASLAND, BOUCK & LEE. INC Privileged and Confidential engineers & scientists DR\FT

7. Introduction and Background

At the request of the General Electric Company (GE), Blasland Bouck & Lee (BBL), ARCADIS, Paul Bernstein1 and Dr. Michael Chamberlain2 studied the presence of mink in a Study Area (described below) within the Housatonic River watershed between the spring of 2001 and the spring of 2002. The objective of this study was to qualitatively determine the presence/absence, abundance, and distribution of free-ranging mink in the Study Area, including areas adjacent to the mainstem of the river and nearby tributaries. The primary methods used to determine the presence of mink were the monitoring of tracks at scent post stations in the spring, summer and fall and in the snow during the winter.

From 1998 to 2000, the U.S. Environmental Protection Agency (EPA) conducted field surveys to characterize the ecology of the Housatonic River and the adjacent floodplain. Field studies consisted of general, reconnaissance-level surveys conducted from March to December of 1998, including direct observation, tracking, scat collection and incidental observations made during the course of other investigations. Surveys were also conducted along three scent post transects for three consecutive nights in mid-December 1998. Mink were not observed in the Study Area during the 1998 field studies, and no mink tracks or scat were observed at any of the scent post stations (TechLaw, 1999). More intensive surveys in 1999 and 2000 included snow tracking and expanded scent post surveys. Snow tracking was conducted in fresh snowfall along 500-meter transects in all habitat types for a minimum of two to three snow events in the winter of 1999 and 2000. In 1999-2000, the EPA observed two sets of mink tracks in the Study Area.

GE's study was designed to assess and document the presence of mink in the Study Area by monitoring mink tracks at scent post stations and in the snow over an extended period of time to determine if mink signs indicate the presence of a resident mink population. In addition, we attempted to trap mink for a radio-telemetry study; however, no mink were captured and this portion of the study was discontinued.

1 Former New York State Department of Environmental Conservation game warden. 2 Assistant Professor of Wildlife Ecology, Louisiana State University

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2. Materials and Methods

This section details the methods employed in the mink population study, including the definition of the Study Area and procedures for observations via scent post station monitoring and transects for snow tracking. This study was initiated in early April 2001 and continued through March of 2002.

2.1 Study Area

The Study Area comprised the mainstem of the Housatonic River and adjacent banks and floodplain areas in Lenox, Berkshire County, between New Lenox Road and Woods Pond, and associated tributaries in the October Mountain State Forest (e.g., Mill Brook, Roaring Brook and Felton Brook) as well as Yokun Brook. The study focused on land with suitable foraging habitat for mink (i.e., irregular shorelines and backwaters with dense, wooded cover near the water).

2.2 Scent Post Stations

One hundred scent post stations were placed in the Study Area (from New Lenox Road south toward, and including, Woods Pond). Seventy stations were constructed along the mainstem of the river, while the remaining 30 were constructed on the river's tributaries. The locations of all scent post stations were logged using GPS. Scent post stations were located in areas close to a natural entrance/exit to the river from the bank (i.e., beaver slide, visible animal run) to increase the likelihood of animal interest and visitation. These scent post stations were installed in June 2001 and monitored on three days every month until December 2001. The scent posts consisted of an approximately one-meter-diameter circle prepared by clearing vegetation and other debris and spreading a manufactured, fine-textured soil/sand over the circle as a tracking medium. One of two possible attractants (lamb's wool soaked with mink urine and amino acid disks) was placed in the center of each scent station. The two attractants were placed at alternating scent post stations along the river and tributaries. In the final month of the scent post station study, mink scat obtained from a nearby mink farm, Berkshire Furs, was used at a subset of stations to replace the other attractants. All observed mink tracks (confirmed and potential) were photographed.

2.3 Snow Tracking/Transects

Between December 2001 and March 2002, site visits were made to monitor the Study Area for mink tracks whenever fresh snow was present. Tracks were also documented when they were observed incidentally during other field activities. Field staff searched for mink tracks along portions of the east and west sides of the River between New Lenox Road and Woods Pond, and along Roaring Brook and Mill Brook, in areas that appeared likely to support mink (e.g., areas around springs, natural dens) and that were accessible by foot. Coverage on the east side of the river was extensive, whereas, due to poor access, there was no coverage of the west side of the river between the Lenox Sportsmen's Club (just south of New Lenox Road) and Woods Pond. The primary areas where transects were walked during these site visits are shown in Figure 1. When tracks were observed, the location was documented using a GPS and photographs of the tracks were taken.

Where possible, the sex of the mink that left the tracks was determined by Paul Bernstein. A determination of the sex of the mink that left the tracks is primarily based on the tracks' size (width and depth) and the length of the stride indicated by the tracks. Males generally leave wider and deeper tracks and take longer strides, due to their larger size. Other factors that must be considered when determining the sex of the mink that left the tracks include the time of year, weather conditions, and the amount and freshness of snow, when winter tracking (as snow melts, tracks can expand in size).

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3. Results

A total of 33 sets of mink tracks were observed in the Study Area during the study period (April 2001 through March 2002). Of the 33 sets of tracks observed in the Study Area during the study period, one set was observed in May 2001 during other field activities and four sets of tracks were observed at scent post stations during station monitoring - three sets in June 2001 and a fourth set in December 2001. The remaining 28 sets of tracks were observed during snow tracking from December 2001 to March 2002 In addition, two sets of mink tracks had been observed incidentally in the Study Area in January 2001 during other field activities prior to the start of the mink study period, for a total of 35 mink tracks observed in the Study Area. In addition to the tracks found in the Study Area during site visits, two additional sets of mink tracks were observed in March 2002 near the confluence of the east and west branches of the Housatonic River, during other field activities. Although these tracks are outside of the Study Area, they provide additional evidence of the presence of local mink. The number of tracks observed, date observed, location, and field notes (including identification of sex, where determined) are provided in Table 1.

The locations of observed tracks relative to scent post stations and transects are shown in Figure 1. More than half (24) of the 35 tracks observed were located on the mainstem of the river (including backwaters and Woods Pond). Eleven sets of tracks were observed along tributaries, including Felton Brook, Mill Brook, and Roaring Brook. Sixteen tracks were identified as belonging to a particular sex.

Male mink tracks, as indicated by their large size, are shown on the left. These tracks were found along the mainstem. Shown on the right are female mink tracks found at a scent post station on the west side of the mainstem of the river next to the Sportsmen's club. Female mink tracks are differentiated from male mink tracks by their smaller size.

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The photo on the left shows mink tracks in the sand found on the west shore of the mainstem. These tracks were not identified to sex.

Mink tracks in snow found near the Old Beaver Lodge on the mainstem are shown on the right These tracks also were not identified to sex.

/

Originals in color.

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4. Discussionand Summary

Between January 2001 and March 2002, 35 sets of mink tracks were observed in the Study Area. Four of these were observed at scent post stations and the remaining tracks were observed in the snow or mud during snow tracking studies or during other field activities. Given the extensive period that the scent post station study was carried out and the obvious presence of mink in the area as indicated by the results of the snow tracking study, it is unclear why so few tracks were observed at scent post stations. We believe that it may have been due to the attractants used at the stations throughout most of the study (mink urine and amino acid disks) or the somewhat artificial nature of the scent post itself- a cleared area with manufactured sand spread to record tracks. In the final month of the scent post station study, mink scat was used as the attractant at a subset of stations and mink tracks were found at one of those stations. Due to poor winter weather conditions, we were unable to conduct the scent post station monitoring in subsequent months using scat, so we were unable to test the increased efficacy of using scat as an attractant.

Nonetheless, several lines of evidence indicate that the tracks observed reveal the presence of a mink population residing in or at least using the Study Area. This evidence includes the presence of clusters of tracks in different reaches of the river observed over a several month period as well as the positive identification of tracks belonging to both male and female mink (Figure 1 and Table 1). Based on his knowledge of mink natural history, including home range and territoriality, Dr. Chamberlain estimates that the observed mink tracks likely indicate the presence of 6 to 10 mink in the Study Area.

Using both the temporal and geographic spacing of the tracks, Dr. Chamberlain concluded that at least two males, two females, and two mink of unknown sex maintain home ranges that include portions of the Study Area. A minimum of two male mink are estimated to have been present because two different sets of male tracks (Tr-36/37 and Tr-33) were recorded within distinctly different stretches of the river in the same sampling period. Based on home range characteristics of mink in riverine systems (Leopold and Chamberlain, 2001; Mitchell, 1961), it is highly unlikely that those tracks were left by the same animal. Similar reasoning dictates that there are at least two females, because female mink tracks (Tr-27 and Tr-29) were detected on nearly opposite ends of the Study Area, approximately a 1900-meter (m) linear distance, within the same sampling period. According to the literature, the probability that those tracks belong to the same female is very low. Linscombe et al. (1982) report that the average distance in stream length for a female home range is 1850 m (stream length, not linear), which is much less than was observed between the two females (linear distance) in the Study Area. Finally, Dr. Chamberlain concluded that at least two other mink of unknown sex were also present in the Study Area, based on the findings of other sets of tracks (Tr. 13 and Tr. 22) in separate areas during the same time period (Tr-13-U distant from Tr-14-F/Tr-15-F/Tr-16-U; Tr-22 distant from Tr-18-U/Tr-19­F/Tr-20-F/Tr-21-F). In order to avoid potential "double-counting," when tracks that could not be identified to sex were located in proximity to tracks identified to sex, the unknown tracks were not assumed to represent a different individual.

In several instances, tracks found fairly large distances from one another were conservatively estimated as belonging to one individual, but may have been left by two different individuals. Assuming that these tracks belonged to a single mink produces a conservative total estimate of 6 mink in the Study Area, whereas assuming such cases may indicate the presence of multiple mink results in a total estimate of 10 mink with home ranges that include the Study Area.

For these reasons, and considering the uncertainties inherent in this type of tracking study (i.e., different substrates, varying weather conditions, observations of tracks up to several days after they were made), Dr. Chamberlain is confident that at least six mink occupy home ranges that include the Study Area, and there may

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be as many as 10 mink occupying a portion of the Study Area. Note, however, that this estimate of 6-10 mink essentially excludes the area on the west side of the river between the Lenox Sportsmen's Club and Woods Pond, which was not surveyed in winter due to poor access. Therefore, this estimate of 6-10 mink likely underestimates the number of mink active in the Study Area.

It is not possible to estimate the optimum mink abundance for the Study Area because such an estimate would need to take into consideration a number of conditions that were not measured, including prey abundance and availability, weather, the presence of conspecific factors, and habitat disturbance. It is worth noting, however, that the estimated number of mink in the Study Area is within the range of mink densities reported in other riverine systems. Studies in Montana and Michigan (Marshall, 1936; Mitchell, 1961) have reported mink densities ranging from one mink per 13 hectares to one mink per 31 hectares. These can be compared with approximately one mink per 20 hectares (assuming 6 mink) to one mink per 12 hectares (assuming 10 mink) in this study. This comparison suggests that, even without considering the area on the west side of the Housatonic River that was not surveyed, the density of mink in the Study Area falls within a range that would be expected based on the literature.

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5. References

Leopold, B. D. and M. J. Chamberlain. 2001. Ecology and management of carnivorous furbearers in the southeast. Pages 248-277 in Wildlife of Southern Forests: Habitat and Management, J.G. Dickson, editor. Hancock House Publishers, Elaine, WA.

Linscombe, G., N. Kinler, and R. J. Aulerich. 1982. Mink. Pages 629-643 in J. A. Chapman and G. A. Feldhamer, editors. Wild mammals of North America: biology, management and economics. Johns Hopkins University Press, Baltimore, MD.

Marshall, W. H. 1936. A study of the winter activity of the mink. Journal of Mammalogy. 17:382-392.

Mitchell, J. L. 1961. Mink movements and populations on a Montana river. Journal of Wildlife Management. 25:48-54.

Roy F. Weston, Inc. 2000. Technical Support Services General Electric (GE) Housatonic River Project: Supplemental Investigation Work Plan for the Lower Housatonic River. Volume I-Text and Figures. Volume II-Appendices. Prepared for U.S. Army Corps of Engineers. West Chester, Pennsylvania.

TechLaw, Inc. 1999. Final Preliminary Ecological Characterization Newell Street to Woods Pond. Volume I-Text. Volume H-Appendices A through B.2. Volume Ill-Appendices B.3 through D. Submitted to EPA. Boston, Massachusetts.

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Table 1. Mink Track Observations

DATE LOCATION 1/18/01 New Lenox Launch 1/18/01 Woods Pond 5/11/01 Mainstem River Bank 6/14/01 Trib Station #17 6/27/01 Trib Station #11 6/28/01 Trib Station #12 12/19/01 MS-18 1/9/02 Roaring BrkRd 1/9/02 Roaring Brk Rd 1/9/02 Main Stem

1/17/02 Roaring BrkRd 1/17/02 MS-37 Backwater 1/17/02 South of MS-48 1/17/02 Big Spring 1/23/02 Roaring Brk Rd 1/23/02 MS-37 Backwater 1/23/02 Mainstem 1/23/02 South Of MS-48 1/23/02 W. Side Mainstem

2/28/02 Mill Brk. Under Roaring BrkRd

2/28/02 Roaring Brk Rd 2/28/02 Mainstem 2/28/02 Mainstem 2/19/02 Roaring Brk Rd Bridge 2/19/02 Mainstem 3/18/02 Mainstem 3/19/02 MS-37 Backwater 3/19/02 MS-52 Walkway 3/19/02 Mainstem 3/19/02 Mainstem

3/19/02 Mainstem 3/19/02 Mainstem

3/21/02 Woods pond footbridge Mink Tracks in snow 3/21/02 Mainstem Mink Tracks in snow 3/21/02 Mainstem Mink Tracks in snow

NOTES NAME Tracks from river to land Tr-1 East side of Woods Pond Tr-25 Male tracks running on mud shore Tr-5 Male tracks in mud - Felton Brk Tr-6 Tracks on station Tr-7 Tracks on station Tr-8 Tracks on sand- scat left/collect Tr-9 Roaring Brk Rd. Bridge over Mill Brk Tr-10 Roaring Brk Bridge Tr-11 Along log on main river (Box 899) Tr-12 Roaring Brk Bridge Tr-13 Female - tracks into river Tr-14 Female - Possible Den Tr-15 Passes through open spring area Tr-16 Roaring Brk Bridge Tr-18 Likely Female, in and out holes Tr-19 Female-in b/w MS-42/44 Tr-20 Same poss. Den location - Fem. Tr-21 Mink trail from river to hole ~20' Tr-22 Male, by mail box #37 Tr-26

Female, running under bridge Tr-27 Male, walkway S of MS-43 Tr-28 Female, same possible den site Tr-29 Male, in and out water & holes Tr-23 Male, in b/w MS-42/44 Tr-24 MS-52 Walkway, visiting animal carcass Tr-31 lope along shore, in/out water Tr-32 Large Male, in/out water Tr-33 Around tree/water by box#899 Tr-34 In mud, on W bank, b/w MS8 and MS9.Tr-35 Possibly same mink as above, running towards above location. 200 yds S of above siting.

Large Male, in/out water, S of Box#711 Tr-36 Large Male, 100 yds S of Box#711.Tr-37 Possibly same mink as above, but at a different location and feeding area.

Large Male, in/out small stream/culvert Tr-38 30 yds W of Box#899, in/out marsh Tr-39 Fem, on MS-17,10' off river bank Tr-41

OBSERVATION Mink Tracks in snow Mink Tracks in snow Mink Tracks in mud Mink Tracks in mud Mink Tracks in sand Mink Tracks in sand Mink Tracks in sand Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow

Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow Mink Tracks in snow

Mink Tracks in snow Mink Tracks in snow

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Tr-1-U Tr-5-M Tr-6-M Tr-7-U Tr-8-U Tr-9-U Tr-10-U Tr-11-U Tr-12-U Tr-13-U Tr-14-F Tr-16-F Tr-16-U Tr-18-U Tr-19-F Tr-20-F Tr-21-F Tr-22-U Tr-23-M Tr-24-M Tr-2S-U Tr-26-M

Legend Figure 1. Mink Track Locations.

Tr-27-F Tr-28-M

Mink Itack locations Tr-29-F Tr-31-U Female Tr-32-u

Housatonic River • Male Tr-33-M-L *

0 Sax unknown Tr-34-U Pimleftd n.d • oufirlnmil Aimuw WaikPiDfhut

Tr-35-U Searching IranEecIl Tr-36-M-L <s& Tr-37-M-L Capproi»imatBB«8tiI of Tr-33-M-L

July 07/02 10 yi floodplain) Tr-39-U g:\gts\housatantc\mtnk_tracks.apr Tr-41-F

1 ppm jeaplelh

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1/18/01 6/11/01 6/14/01 6/27/01 6/28/01 12/19/01 1/9/02 1/9/02 1/9/02 1/17/02 1/17/02 1/17/02 1/17/02 1/23/02 1/23/02 1/23/02 1/23/02 1/23/02 2/19/02 2/19/02 1/18/01 2/28/02 2/28/02 2/28/02 2/28/02 3/18/02 3/19/02 3/19/02 3/19/02 3/19/02 3/19/02 3/19/02 3/21/02 3/21/02 3/21/02

Tracks from river to land Male tracks running on mud shore Male tracks in mud - Felton Brk Tracks on station Tracks on station Tracks on sand- scat left/collect Roaring Brk Rd Bridge over Mill Brk Roaring Brk Bridge Along log on main nverfBox 899) Roaring Brk Bridge Female - tracks into river Female - Possible Den Passes through open spnng area Roaring Brk Bridge Likely Female, in and out holes Female-in b/w MS-42/44 Same poss Den location - Fern Mink trail from river to hole -20' Male, in and out water 8 holes Mate, in b/w MS-12/44 East side of Woods Pond Male, bymaii box #37 Female, running under bridge Male, walkway S of MS-43 Female, same possible den site MS-52 Walkway, visiting animal carcass lope along shore, in/out water Large Male, in/out water Around tree/water by box#899 In mud. on W bank, b/w MS8 and MS9 Large Male, in/out water. S ofBox#711 Large Male, 100 yds S of Box«711 Large Male, in/out small stream/culvert 30 yds W of Box#899, in/out marsh Fem, on MS-17, 10' off river bank

Original includes color coding.