2008 NORTHEASTERN NATURALIST 15(1):13–24
Survival and Post-release Movements of River Otters
Translocated to Western New York
Romeo M. Spinola1,3,*, Thomas L. Serfass2, and Robert P. Brooks1
Abstract - Survival and post-release movements of individuals translocated for
reintroduction purposes have implications for intra-specific interactions, which
are essential for reproduction, and, ultimately, for the success of the reintroduction
effort. Between 1997–1998, 28 (14M:14F) Lontra canadensis (river otters) were
translocated to the Genesee River, NY, to restore extirpated populations. Otters
were implanted with transmitters to determine survival, cause of mortality, and
post-release movements. Five (3M:2F) otters died during the study: three (2M:1F)
mortalities were caused by collisions with vehicles and two (1M:1F) were from
unknown causes. Survival rate during the first year was 0.89 (95% CI = 0.78–1.00);
annual survival rate was 0.92 (95% CI = 0.79–1.00) and 0.86 (95% CI = 0.70–1.00)
for males and females, respectively. Post-release dispersal distance of 22 (11M:
11F) otters ranged from 1.2 to 54.0 km (mean = 12.5 km, 95% CI = 8.5–23.7 km).
Dispersal distance of females was greater than that of males by a mean of 8.7 km
(95% CI = 0.1–19.2 km). River otters that dispersed >15 km from the release site
experienced higher mortality.
Reintroductions are a common management tool to restore extirpated
Lontra canadensis Schreber (river otters) populations (Ralls 1990). These
programs are expensive and often involve the release of a limited number of
individuals, as releasing larger groups of individuals has been shown to do
little to increase translocation success (Griffith et al. 1989). However, small
populations are susceptible to deleterious consequences of environmental
and demographic stochasticity and inbreeding (Caughley and Sinclair 1994).
Consequently, a primary goal of reintroduction programs should be to maximize
initial population growth to minimize impacts of stochastic events
(Komers and Curman 2000). Therefore, reintroduction programs ideally
should seek to establish high levels of reproduction and survival by translocated
individuals to enhance likelihood of a successful project.
Intra-specific interactions, essential for enhancing reproductive opportunities
in a newly reintroduced population, depend on the survival and
post-release movements of translocated individuals. For example, high postrelease
mortality reduces the number of reproducing individuals. Similarly,
extreme post-release movements away from the release area reduce the
1Penn State Cooperative Wetlands Center, The Pennsylvania State University, University
Park, PA 16802. 2Department of Biology, Frostburg State University, Frostburg, MD
21532. 3Current address - Instituto Internacional en Conservación y Manejo de Vida
Silvestre, Universidad Nacional, Apartado 1350-3000, Heredia, Costa Rica. *Corresponding
author - email@example.com.
14 Northeastern Naturalist Vol. 15, No. 1
opportunity for intra-specific interactions, which may lessen the extent of
breeding activity among translocated individuals (Erickson and McCullough
1987). Thus, understanding factors affecting survival (i.e., identifying causes
of mortality) and examining issues influencing post-release movements are
crucial to improving the chances of success in reintroduction efforts. Also,
empirical estimates of survival and post-release movements are important in
viability analyses of reintroduced populations (White 2001).
Previous studies suggest survival of translocated river otters is affected
by the extent of post-release movements. In Missouri, otters that dispersed
farther from the release site experienced higher human-caused mortality
than individuals that remained closer to the release site (Erickson and Mc-
Cullough 1987). In Indiana, 2 of 5 otters that died less than 1 year post-release had
dispersed 66 and 27 km, reaching sites outside of the primary restoration
area (Johnson and Berkley 1999). River otters are capable of extensive
post-release movements (Erickson and McCullough 1987, Johnson and
Berkley 1999), which increase their likelihood of encountering sub-optimal
conditions and higher levels of mortality as they emigrate from the primary
restoration area. Thus, reintroduction projects should use a continuum of
high quality aquatic habitats to minimize human-caused mortalities (e.g.,
accidental trapping and collisions with cars) during initial movement of
Post-release movements in otters are likely to be influenced by their mating
system. Otters are polygynous (Estes 1989, Toweill and Tabor 1982);
thus, male spatial pattern is expected to change during the breeding season
to maximize mating opportunities (Sandell 1989). Consequently, travel distances
of males are predicted to increase substantially during that season.
Historically, the river otter occurred in all watersheds of New York (Hall
1981). However, during the 1800s, river otter populations started to decline
in some regions of the state and became extirpated from many areas (Gotie
et al. 1994). As a result, river otter populations remained mainly in upstate
New York, east of the Unadilla River and north of the Mohawk Valley (Gotie
et al. 1994). In 1995, a river otter reintroduction program was implemented
to restore river otter populations to central and western New York.
Documenting fates of translocated individuals is important to evaluate
the short-term success of the reintroduction effort and to improve the success
of future translocations. Despite this, little information has been published
on survival and post-release movements in reintroduced otter populations. In
this study, we analyzed survival and post-release movements of river otters
translocated to the Genesee River in western New York, where otters have
been completely extirpated. Our objectives were to 1) estimate survival rates,
2) assess causes of mortality, and 3) describe post-release movements.
The study area (ca. 1882 km2) is located in the upper Genesee River
watershed and includes portions of Wyoming, Livingston, and Allegany
2008 R.M. Spinola, T.L. Serfass, and R.P. Brooks 15
counties in western New York (Fig. 1). The area is dominated by agricultural
activities interspersed with residential developments. The landscape consists
of rolling hills with most communities and major roads in the valleys.
The upper Genesee River watershed contains 2297 km of riverine habitats
and 51.3 km2 of lentic habitats including emergent wetlands, lakes, Castor
canadensis Kuhl (beaver) impoundments, and man-made ponds. Mean size
of lentic patches (n = 2363) was 2.2 ha (SD = 13.2; data were obtained with
ArcView 3.2, Environmental Systems Research Institute, Inc., Redlands,
CA), which are scattered in the agricultural/development matrix on land
cover/land-use coverage digitized for the study area. Average temperatures
range from -5.2 °C in January to 21.1 °C in July, with an average annual
precipitation of 741 mm and average annual snow fall of 1008 mm (USDA
1999). The region typically is covered with snow from late December to
River otters were released at 2 sites on the Genesee River in 1997 and
1998 (Fig. 1). The first was located at Lee’s Landing inside 7000-ha Letchworth
State Park (LSP). The park includes about 30 km of the Genesee
River, which flows through a steep canyon, extending from a series of 3
waterfalls to the Mount Morris Federal Flood Control Dam. Most of the
riparian habitat along the Genesee River within LSP has been disturbed by
periodic flooding caused by regulation of water levels in the dam. The second
site was located on private property at the confluence of Wiscoy Creek
and the Genesee River, 18 km upstream of the LSP site. Riparian habitat in
this portion of the Genesee River watershed has been degraded by human
use, particularly farming.
Figure 1. Otter release sites on the Genesee River and dispersal locations of 20 otters
in western New York, 1997–1998. Two otters are not displayed because they dispersed
beyond the area represented by the map.
16 Northeastern Naturalist Vol. 15, No. 1
Capture, handling, and release
Trappers trained to participate in the New York River Otter Project
(NYROP) used foot-hold traps sizes #1 to #2 and #11 to capture river otters
in the Adirondack and Catskill regions of New York. Prior to release, all
otters underwent a captive management program at Cornell University or
The Pennsylvania State University, in which veterinarians provided physical
and health evaluations and performed surgeries to implant radio-transmitters
(Hernandez-Divers et al. 2001, Serfass et al. 1993). Transmitters were
placed into the peritoneal cavity following established surgical procedures
and post-operative protocols (Hernandez-Divers et al. 2001, Serfass et al.
1993). Typically, otters were held in captivity for 7–15 days prior to implanting
transmitters, followed by a post-surgical convalescent period of about 7
days. All capture and handling procedures were approved by the Institutional
Animal Care and Use Committee at The Pennsylvania State University (Permit
No. 91R1583D096) and Cornell University (Permit No. 94-108-03).
At the LSP site, 14 (8M:6F) and 6 (3M:3F) otters were released in 1997
and 1998, respectively. Eight (3M:5F) otters were also released at the Wiscoy
Creek site in 1998. Except for 4 otters (3M:1F) released in July 1997,
all releases occurred in October and November. All released river otters were
adults assumed to be based on tooth wear and size (body mass and length).
Each otter was equipped with an implantable transmitter (IMP-200;
Telonics, Inc. Mesa, AZ) in the 164–165 MHz range with an expected
operational life of 10 mo. During radiotracking, river otters initially were
located from a vehicle with a TR-2 receiver (Telonics, Inc.) and an omnidirectional
whip antenna. When a signal was detected, the location of the
animal was determined by using an “H” antenna and walking to the signal
(homing) without relying on triangulation data (White and Garrot 1990).
Locations were plotted on 1:24,000 scale topographic maps and digitized
using ArcView 3.2 to create a GIS database.
We attempted to locate otters daily, but frequency varied with seasonal
conditions and access to areas occupied by otters. When otters could not be
located by ground tracking, we flew in a single engine airplane (Piper PA-
22-150) equipped with an omnidirectional whip antenna. Specific locations
of “relocated” otters were then determined by ground tracking immediately
after the flight.
We determined if an otter died by radio-monitoring and by verifying
reports of road-killed otters reported to the New York State Department
of Environmental Conservation (NYS-DEC). We considered an otter to
be inactive when signal strength was consistent during the first 60 sec of a
radio-monitoring session. If an inactive signal was recorded from the same
location during several days, we intensified the monitoring to determine if
2008 R.M. Spinola, T.L. Serfass, and R.P. Brooks 17
the animal was alive. If we suspected that the animal was dead, we made all
possible efforts to recover the carcass. Recovered carcasses were sent to the
College of Veterinary Sciences at Cornell University for necropsy.
We estimated survival functions and annual survival rates with the
staggered-entry Kaplan-Meier method (Pollock et al. 1989a, b). We rightcensored
(i.e., eliminated the individual for the subsequent analysis) a river
otter after losing radio contact with it, assuming it had either left the study
area or had an inoperable transmitter. The survival function was calculated
for 64 weekly exposure periods. The log-rank test (Pollock et al. 1989b)
with 1 degree of freedom was used to compare the survival function between
river otters translocated in 1997 and 1998, and between sexes for a
period of 64 weeks. We estimated 95% confidence intervals for survival
rates based on a log-normal distribution. The lower and upper confidence
limits were computed as:
We measured movements of river otters as the net displacement between
radio-locations taken 2–3 days apart. Distances were obtained with the “create
polyline from point file” function in the Animal Movement Extension for
ArcView (Hooge and Eichenlaub 1997).
We analyzed mean distance moved for males and females using a 2 x 5
factorial design. The two factors were sex, with 2 levels (male and female),
and season, with 5 levels (Fall I, Winter I, Spring I, Summer I, Fall II; see
next section—remarks on data pooling and seasons definition). We used a
linear mixed model to account for repeated measures and individuals with
missing data to examine the influence of sex and season in the extent of otter
movements (Littell et al. 1998). We used a first-order autoregressive variance-
covariance structure to specify the variance-covariance matrix for the
within-subject effect. We conducted pairwise comparisons for those terms
in the model that were significant, adjusting the confidence intervals for
the effect size with the Bonferroni method. Distance data were transformed
using natural logarithms to meet assumptions of homogeneity of variance
(Cochran C19 = 0.13, P = 0.677) and normality.
To measure post-release dispersal, we measured the linear distance from
the release site to the arithmetic mean of radio-locations observed during the
last season the river otter was monitored. Only those otters that were monitored
until the transmitter battery expired (n = 17) or known to have died
during the study (n = 5) were included in calculating post-release dispersal.
18 Northeastern Naturalist Vol. 15, No. 1
We estimated 95% confidence intervals of means and the mean difference
(effect size) by bootstrapping based on the 2.5 and 97.5 percentiles of
1000 replicates. We compared the post-release dispersal distances between
males and females using multi-response permutation procedure (MRPP) for
univariate-grouped data analogous to the t-test. The MRPP is based on distance
functions and does not assume any population distribution (Cade and
Remarks on data pooling and seasons definition
Data on post-release movements for 1997 and 1998 were pooled because
of insufficient sample sizes (Anderson et al. 2001). Seasons were defined
by calendar months (fall: September 21–December 20; winter: December
21–March 20; spring: March 21–June 20; summer: June 21–September 20).
Roman numerals as suffix were used to denote a specific season to group
animals based on their first or second season regardless of actual year of
release. Fall I included data collected during fall 1997 and 1998 for river
otters released in 1997 and 1998, respectively; Winter I included data collected
during winter 1998 and 1999 for river otters released in 1997 and
1998, respectively; Spring I included data collected during spring of 1998
and 1999 for river otters released in 1997 and 1998, respectively; Summer I
included data collected during summer of 1998 and 1999 for river otters released
in 1997 and 1998, respectively; Fall II included data collected during
fall of 1998 and 1999 for river otters released in 1997 and 1998, respectively.
Spring was considered to be the breeding season of river otters (Hamilton
and Eadie 1964, Melquist and Hornocker 1983, Toweill and Tabor 1982).
Remarks on statistical analysis
We used an alpha level of 0.05 for all statistical analyses. The linear
mixed model for repeated measures was conducted using PROC MIXED
- SAS (SAS Institute Inc., Cary, NC). Data transformation and tests for
homogeneity of variance and normality were conducted with R (R Development
Core Team 2004). The bootstrapping procedures were performed with
S-Plus 6.1 for Windows (Insightful Corporation, Seattle, WA). The multiple
response permutation procedure (MRPP) was performed with Blossom Version
W2001.07t (Midcontinent Ecological Science Center, US Geological
Survey, Fort Collins, CO).
Five (3M:2F) of 28 translocated otters died during the study. Three
mortalities were caused by collisions with vehicles: F790 was struck by a
vehicle 37 km north of the release site in March 1998 (5 months post-release),
M180 was road-killed 17 km northwest of the release site in March 1999 (19
months post-release), and M590 was killed in a collision with a vehicle 15
km southeast of the release site in March 2000 (32 months post-release). All
vehicle-related mortalities were associated with long-distance dispersal from
2008 R.M. Spinola, T.L. Serfass, and R.P. Brooks 19
the release site. The other two mortalities were of unknown causes. The transmitter
from M730 was recovered from a beaver pond 5 km west of the release
site 10 months post-release, and Female F240 was also found dead in a beaver
pond 3.7 km south of the release site in January 2000 (14 months after being
released); cause was undetermined for both deaths.
Annual survival rate for translocated river otters was 0.89 (95% CI=
0.78–1.0) for both sexes combined, 0.92 (95% CI = 0.79–1.0) for males, and
0.86 (95% CI = 0.70–1.0) for females. Survival rates did not differ between
1 = 0.18, P = 0.67) or sexes (χ2
1 = 0.32, P = 0.57). M180 and M590
were killed after the monitoring periods of 52 and 64 weeks considered for
the estimation of annual survival rate and survival function, respectively.
Consequently, those mortalities were not included in both estimations.
We measured 1297 distances moved for the 28 translocated otters. Mean
number of distances was 47.5 (SD = 20.9, range = 15–87) and 45.1 (SD =
23.2, range = 16–94) for males and females, respectively. Distances varied
seasonally from 0.53 to 1.60 km for males and from 0.55 to 0.89 km for
females (Table 1). Maximum linear distance between locations was 17.5
and 9.3 km for male M320 and female F080, respectively. These movements
occurred during the first post-release spring and fall for M320 and F080,
respectively. The largest mean distance moved for males occurred in the
breeding season (Spring I); however, for females, distances were greatest
in Fall I (just after being released). Lowest mean distances for both sexes
occurred in Fall II (Table 1). Movements did not differ between males and
females (F(1,70) = 0.38, P = 0.537), and there was no interaction between
sex and season (F(4,70) = 0.31, P = 0.867). However, movements differed by
season (F(4,70 )= 3.92, P = 0.006). Pairwise comparisons among all means for
seasons showed movements were greater in Fall I than in Fall II, but identified no other differences in movements between seasons (Table 2).
Post-release dispersal of 22 (11M:11F) otters ranged from 1.2 to 54.0 km
(Figs. 1and 2), with a mean of 12.5 km (95% CI = 8.5–23.7 km). Mean postrelease
dispersal distance was 8.1 km (95% CI = 6.0–13.5 km) for males and
16.8 km (95% CI = 8.9–37.5 km) for females and was greater for females
than for males (δ = 10.845, P = 0.0532) by a mean of 8.7 km (95% CI =
Table 1. Seasonal mean distance (km) between radio-locations 2–3 days apart of male and female
river otters translocated to the Genesee River in western New York, 1997–1999.
Season Mean 95% CI n Mean 95% CI n
Fall I 1.26 0.79–2.48 10 0.89 0.58–1.33 13
Winter I 0.79 0.34–1.80 9 0.61 0.27–1.37 13
Spring I 1.60 0.98–2.59 13 0.74 0.45–1.87 10
Summer I 0.77 0.35–1.16 10 0.85 0.39–1.85 10
Fall II 0.53 0.15–1.11 8 0.55 0.29–0.93 10
Overall 1.049 0.80–1.30 14 0.73 0.56–0.90 14
20 Northeastern Naturalist Vol. 15, No. 1
Seventeen (77%) of 22 otters dispersed <15 km from the release site.
Two (12%) of these died, whereas 3 (60%) of the 5 otters that dispersed
greater than 15 km died. The proportion of dead otters was greater for the otters that
dispersed >15 km than the otters that dispersed <15 km (χ2 = 5.1186, df =
1, P = 0.0237). The greatest dispersal distances from the release site were
21.3, 37.0, and 54.0 km for 3 females.
Our high annual first-year survival rate (89%) was similar to that
reported for otters translocated to Missouri (81%; Erickson et al. 1984),
Pennsylvania (83%; Serfass et al. 1986), Tennessee (91%; Griess 1987),
and Indiana (71%; Johnson and Berkley 1999). Lower survival rates
Table 2. Comparisons among seasonal mean distance (km) between radio-locations 2–3 days
apart of male and female river otters translocated to the Genesee River in western New York,
1997–1999. Back-transforming the mean difference on the log-scale corresponds to a ratio of
the medians on the original scale. For example, the first comparison resulted in a ratio of 2.95.
This means that the median extent of movements during Fall I was 2.95 times that of the median
of Winter I.
Comparison Ratio 95% Confidence IntervalA
Fall I–Winter I 2.95 0.76–11.45
Fall I–Spring I 1.26 0.29–5.50
Fall I–Summer I 2.45 0.52–11.47
Fall I–Fall II 6.22 1.25–31.03
Winter I–Spring I 0.43 0.11–1.70
Winter I–Summer I 0.83 0.18–3.91
Winter I–Fall II 2.11 0.41–10.74
Spring I–Summer I 1.94 0.49–7.66
Spring I–Fall II 4.93 1.03–23.48
Summer I–Fall II 2.54 0.60–10.73
AAdjusted with the Bonferroni method.
Figure 2. Postrelease
distance (km) of
22 river otters
translocated to the
2008 R.M. Spinola, T.L. Serfass, and R.P. Brooks 21
occurred in otters translocated to Ohio (46%; McDonald 1989), Oklahoma
(60%; Hoover et al. 1984), and West Virginia (56.7%; Tango et al. 1991).
In most river otter translocation projects, stress-related mortalities occurred
shortly after release. In contrast, necropsies for the found carcasses
and the timing of mortality of the 5 otters that died during our study yielded
no evidence to suggest that capture, transport, captive management, or implantation
of transmitters contributed to the mortalities.
We believe our captive management program was beneficial to river
otters and may have increased their post-release survival. The program
facilitated treatment of trap-related injuries, recovery from stress caused
by capture and handling (Rothschild 2005), and recovery from surgeries
to implant transmitters. A captive management program also enhances the
opportunity to detect communicable diseases, such as rabies (Serfass et al.
1995). We recommend other river otter reintroduction projects incorporate
similar programs with veterinary supervision into their project protocol.
Three of our five mortalities were vehicle-related and coincided with a
noticeable change in otter spacing patterns in late winter and early spring,
the peak period for reproductive activity. Movements of river otters during
this period may be influenced by easier access to new habitats because of ice
melt and increased opportunities to enhance reproductive success (i.e., males
searching for females). In addition, vehicle-related mortality was greater in
otters that dispersed extensive distances from release sites. As individuals
move greater distances, they encountered sub-optimal habitats and mortality
factors associated with human-dominated landscapes. Although release
areas were selected to minimize these impacts, habitat conditions and human
activities in surrounding aeas differed from those in release areas. Thus, conflicts related to human activities (e.g., accidental trapping and collision with
vehicles) are more likely in river otters displaying long-distance dispersal.
Similar fates were reported for otters released in Missouri (Erickson and
McCullough 1987) and Indiana (Johnson and Berkley 1999).
Movements were greater immediately after release and, excluding males
in breeding season, typically decreased thereafter. We suspect this change
was related to exploratory movements as newly released otters searched for
denning, resting, and foraging sites. Accordingly, establishment and development
of a home range by otters coincided with more restricted movement
patterns (Spínola 2003).
Post-release dispersal distances displayed by translocated river otters
were likely affected by habitat characteristics. The wide range in dispersal
distances may be due to the patchiness of suitable aquatic habitats along the
Genesee River. Most translocated otters left the Genesee River and LSP to
inhabit a mosaic of isolated patches of aquatic habitats dispersed throughout
a landscape dominated by agricultural activities. Otters often traveled long
distances to reach these habitats. In Missouri, Erickson and McCullough
(1987) reported shorter dispersal distances for otters released in a palustrine
wetland than for those released in a riverine system.
22 Northeastern Naturalist Vol. 15, No. 1
Overall, female river otters dispersed farther than males. We suspect
these differences were related to the habitat and spatial pattern requirements
of females compared to males. Considering that female river otters carry
out the parental care alone, it would be expected that females would occupy
higher-quality habitats than males and, thus, travel greater distance after being
released in search of appropriate areas. Also, female river otters, unlike
males, displayed intra-sexual territoriality (Spinola 2003). These conditions
combine to impose specific requirements on habitats and space to enable
females to locate high-quality habitats and secluded areas to raise young and
avoid conspecific females.
The density and distribution of roads in the aquatic-landscape matrix
may cause significant mortality among river otters traveling overland. Otters
may be more vulnerable to vehicle-related mortality in late winter and spring
when movement patterns change, probably in response to breeding and parturition.
Males may be particularly vulnerable because they travel farther
searching for opportunities to breed. Suitable otter habitats in human-dominated
landscapes are disjunct, which may impose greater overland travel,
thereby increasing the likelihood of vehicle-related mortality. Because most
otter reintroduction programs release few individuals per site, high levels of
survival are important to enhance the likelihood of establishing a population.
Based on our study, the density and distribution of roads should be considered
when evaluating the suitability of a release site.
We thank the Pennsylvania State Cooperative Wetlands Center, the New York
River Otter Project, the New York State Department of Environmental Conservation,
the Pennsylvania Wild Resource Conservation Fund, the US Army Corp of Engineers,
and the New York State Office of Parks, Recreation, and Historic Preservation.
We also thank Dr. G. Kollias and the veterinarian staff from Cornell University, and
T. Blakenship from Pennsylvania State University for implanting transmitters. Bruce
Penrod, Dennis Money, and June Summers provided support, and “Chuck” Green
and Robin Holevinsky assisted in field work. Finally, we thank the Rob and Bessie
Welder Wildlife Foundation from Texas for providing a fellowship to R.M. Spinola.
Anderson, D.R., K.P. Burnham, W.R. Gould, and S. Cherry. 2001. Concerns about
finding effects that are actually spurious. Wildlife Society Bulletin 29:311–316.
Cade, B.S., and J. Richards. 1999. User Manual for BLOSSOM Statistical Software.
Midcontinent Ecological Science Center, US Geological Survey, Fort Collins, CO.
Caughley, G., and A.R.E. Sinclair. 1994. Wildlife Ecology and Management. Blackwell
Scientific Publications, Boston, MA. 334 pp.
Erickson, D.E., and C.R. McCullough. 1987. Fates of translocated river otters in
Missouri. Wildlife Society Bullletin 15:511–517.
Erickson, D.E., C.R. McCullough, and W.R. Porath. 1984. Evaluation of experimental
river otter reintroductions. Final Report. Missouri Department of
Conservation. Federal Aid Project No. W-13-R-38. 46 pp.
2008 R.M. Spinola, T.L. Serfass, and R.P. Brooks 23
Estes, J.A. 1989. Adaptations for aquatic living by carnivores. Pp. 242–282, In J.L.
Gittleman (Ed.). Carnivore Behavior, Ecology, and Evolution. Cornell University
Press, New York, NY. 600 pp.
Gotie, R.F., B. Penrod, and E.M. Ermer. 1994. Restoration of the river otter in central
and western New York. Project proposal. New York State Department of Environmental
Conservation, Bureau of Wildlife, Bath, NY. 35 pp.
Griess, J.M. 1987. River otter reintroduction in Great Smokey Mountains National
Park. M.Sc. Thesis. University of Tennessee, Knoxville, TN. 109 pp.
Griffith, B., J.M. Scott, J.W. Carpenter, and C. Reed. 1989. Translocation as a species
conservation tool: Status and strategy. Science 245:477–480.
Hall, E. 1981. The Mammals of North America. Second Edition. John Wiley and
Sons. New York, NY. 1271 pp.
Hamilton, W.J., and W.R. Eadie. 1964. Reproduction in the otter, Lutra canadensis.
Journal of Mammalogy 45:242–252.
Hernandez-Divers, S.M., G.V. Kollias, N. Abou-Madi, and B.K. Hartup. 2001. Surgical
technique for intra-abdominal radiotransmitter placement in North American
river otters (Lontra canadensis). Journal of Zoo and Wildlife Medicine 32:
Hooge, P.N., and B. Eichenlaub. 1997. Animal movement extension to ArcView. ver.
1.1. Alaska Biological Science Center, US Geological Survey, Anchorage, AK.
Hoover, J.P., C.R. Root, and M.A. Zimmer. 1984. Clinical evaluation of American
river otters in a reintroduction study. Journal of the American Veterinary Medical
Johnson, S.A., and K.A. Berkley. 1999. Restoring river otters in Indiana. Wildlife
Society Bulletin 27:419–427.
Komers, P.E., and G.P. Curman. 2000. The effect of demographic characteristics on
the success of ungulate re-introductions. Biological Conservation 93:187–193.
Littell, R.C., P.R Henry, and C.B. Ammermann. 1998. Statistical analysis of repeated
measures data using SAS procedures. Journal of Animal Science 76:1216–1231.
McDonald, K.P. 1989. Survival, home range, movements, habitat use, and feeding
habits of reintroduced river otters in Ohio. M.Sc. Thesis. Ohio State University,
Columbus, OH. 142 pp.
Melquist, W.E., and M.G. Hornocker. 1983. Ecology of river otters in west-central
Idaho. Wildlife Monographs 83:1–60.
Pollock, K.H., S.R. Winterstein, C.M. Bunck, and P.D. Curtis. 1989a. Survival
analysis in telemetry studies: The staggered entry design. Journal of Wildlife
Pollock, K.H., S.R. Winterstein, and M.J. Conroy. 1989b. Estimation and analysis of
survival distributions for radiotagged animals. Biometrics 45:99–109.
R Development Core Team. 2004. R: A Language and Environment for Statistical
Computing. R Foundation for Statistical Computing, Vienna, Austria.
Ralls, K. 1990. Reintroductions. Pp. 20–21, In P. Foster-Turley, S, Macdonald, and
C. Mason (Eds.). Otters: An Action Plan for their Conservation. IUCN/SSC Otter
Specialist Group, Gland, Switzerland. 126 pp.
Rothschild, D. 2005. Fecal Glucocorticoids: A non-invasive method of measuring
stress in river otters. M.Sc. Thesis. Frostburg State University, Frostburg, MD.
Sandell, M. 1989. The mating tactics and spacing patterns of solitary carnivores. Pp.
164–182, In J.L. Gittleman (Ed.). Carnivore Behavior, Ecology, and Evolution.
Cornell University Press, New York, NY. 600 pp.
24 Northeastern Naturalist Vol. 15, No. 1
Serfass, T.L., L.M. Rymon, and J.D. Hassinger. 1986. Development and progress of
Pennsylvania’s river otter reintroduction program. Pp. 322–342, In S.K. Majumdar,
F.J. Brenner, and A.F. Rhoads (Eds.). Endangered and Threatened Species
Programs in Pennsylvania and Other States: Causes, Issues, and Management.
Pennsylvania Academy of Science, Easton, PA. 519 pp.
Serfass, T.L., R.L. Peper, M.T. Whary, and R.P. Brooks. 1993. River otter (Lutra
canadensis) reintroduction in Pennsylvania: Prerelease care and clinical-evaluation.
Journal of Zoo Wildlife Medicine 24:28–40.
Serfass, T.L., M.T. Whary, R.L. Peper, R.P. Brooks, T.J. Swimley, W.R. Lawrence,
and C.E. Rupprect. 1995. Rabies in a river otter intended for reintroduction.
Journal of Zoo and Wildlife Medicine 26:311–314.
Spinola, R.M. 2003. Spatio-temporal ecology of river otter translocated to western
New York. Ph.D. Dissertation. The Pennsylvania State University, State College,
PA. 125 pp.
Tango, P.J., E.D. Michael, and J.I. Cromer. 1991. Survival and seasonal movements
during river otter restoration efforts in West Virginia. Proceedings of the Annual
Conference of Southeast Association of Fish and Wildlife Agencies 45:64–72.
Toweill, D.E., and J.E. Tabor. 1982. River otter: Lutra canadensis. Pp. 688–703, In
J.A. Champman and G.A. Feldhamer (Eds.). Wild Mammals of North America:
Biology, Management, and Economics. John Hopkins University Press, Baltimore,
MD. 1147 pp.
United States Department of Agriculture (USDA). 1999. Natural Resources Conservation
Center - National Water and Climate Center. Available online at ftp:
//ftp.wcc.nrcs.usda.gov/support/climate/wetlands/ny/36051.txt. Accessed 15
White, G.C. 2001. Why take calculus? Rigor in wildlife management. Wildlife Society
White, G.C., and R.A. Garrot. 1990. Analysis of Radio-tracking Data. Academic
Press, Inc., San Diego, CA. 383 pp.