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Habitat selection by river otters (Lontra canadensis) under contrasting land use regimes

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Habitat preferences of river otters (Lontra canadensis (Schreber, 1777)) are well known, but because most studies were conducted in regions with markedly low or high levels of anthropogenic disturbances, it is not well known how their habitat usage is affected by varied anthropogenic disturbances and land-use regimes on a regional scale. We studied habitat use by otters in eastern New Brunswick, Canada, in an area having both protected and disturbed riparian habitats. Using long-range winter riparian transects, we documented activity-sign distribution along riverbanks in relation to 12 habitat factors and 9 categories of anthropogenic disturbances. We documented variables at site with activity signs and at habitat stations along riverbanks at 500 m intervals. We used logistical regressions and Akaike’s information criterion in an information–theoretic approach to compare models and determine the important factors involved. Habitat-related factors were more important than anthropogenic ones in describing habitat use. The best performing models were those incorporating both habitat and anthropogenic factors. Beaver (Castor canadensis Kuhl, 1820) ponds were the most important habitat factor, while fields were the most important anthropogenic factor. Our results indicate that otters responded mostly to the presence of habitat features they use and secondarily to the presence of anthropogenic structures or activities in an area.
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Habitat selection by river otters
(Lontra canadensis) under contrasting land-use
regimes
D. Gallant, L. Vasseur, M. Dumond, E. Tremblay, and C.H. Be
´rube
´
Abstract: Habitat preferences of river otters (Lontra canadensis (Schreber, 1777)) are well known, but because most stud-
ies were conducted in regions with markedly low or high levels of anthropogenic disturbances, it is not well known how
their habitat usage is affected by varied anthropogenic disturbances and land-use regimes on a regional scale. We studied
habitat use by otters in eastern New Brunswick, Canada, in an area having both protected and disturbed riparian habitats.
Using long-range winter riparian transects, we documented activity-sign distribution along riverbanks in relation to 12 hab-
itat factors and 9 categories of anthropogenic disturbances. We documented variables at site with activity signs and at hab-
itat stations along riverbanks at 500 m intervals. We used logistical regressions and Akaike’s information criterion in an
information–theoretic approach to compare models and determine the important factors involved. Habitat-related factors
were more important than anthropogenic ones in describing habitat use. The best performing models were those incorpo-
rating both habitat and anthropogenic factors. Beaver (Castor canadensis Kuhl, 1820) ponds were the most important habi-
tat factor, while fields were the most important anthropogenic factor. Our results indicate that otters responded mostly to
the presence of habitat features they use and secondarily to the presence of anthropogenic structures or activities in an area.
Re
´sume
´:La pre
´fe
´rence d’habitat de la loutre de rivie
`re (Lontra canadensis (Schreber, 1777)) est bien connue, mais la
majorite
´des e
´tudes furent effectue
´es dans des re
´gions ayant de tre
`s faibles ou de tre
`s fortes perturbations humaines. Par
conse
´quent, nous connaissons mal comment son utilisation de l’habitat est influence
´ea
`l’e
´chelle re
´gionale par les diverses
perturbations anthropiques et utilisations des terres. Nous avons e
´tudie
´l’utilisation de l’habitat par la loutre dans l’est du
Nouveau-Brunswick, au Canada, dans une re
´gion ayant a
`la fois des zones riveraines prote
´ge
´es et perturbe
´es. En effectuant
des transects riverains hivernaux a
`grande e
´chelle, nous avons de
´termine
´la re
´partition des signes d’activite
´des loutres le
long des rivie
`res en fonction de 12 caracte
´ristiques de l’habitat et 9 cate
´gories de perturbations humaines. Nous avons note
´
ces variables aux sites pre
´sentant des signes d’activite
´et aux stations d’habitat a
`intervalles de 500 m le long de la rive.
Nous avons utilise
´des re
´gressions logistiques et le crite
`re d’information d’Akaike dans une approche axe
´e sur la the
´orie
de l’information pour comparer diffe
´rents mode
`les et de
´terminer les facteurs les plus importants. Les facteurs lie
´s aux car-
acte
´ristiques de l’habitat jouaient un plus grand ro
ˆle que ceux lie
´s aux perturbations humaines dans la description de l’uti-
lisation de l’habitat par la loutre. Les mode
`les les plus performants e
´taient ceux qui incorporent a
`la fois des facteurs lie
´s
aux caracte
´ristiques de l’habitat et aux perturbations humaines. Les e
´tangs de castor (Castor canadensis Kuhl, 1820)
e
´taient le facteur de l’habitat le plus important, tandis que les champs repre
´sentaient le facteur de perturbation humaine le
plus important. Nos re
´sultats indiquent que la loutre re
´agit principalement aux caracte
´ristiques de l’habitat dont elle fait us-
age et secondairement a
`la pre
´sence de perturbations ou d’activite
´s humaines dans la re
´gion.
Introduction
Several otter species across the world are considered of
conservation concerns owing to their significant decline
(e.g., Carter and Rosas 1997; Reuther 1999; Gonza
´lez and
Utrera 2004; Loy 2005). In North America, river otters
(Lontra canadensis (Schreber, 1777)) were extirpated from
many regions of its historic range (Melquist and Dronkert
1987) and numerous reintroduction projects and monitoring
activities have been implemented to restore the situation
(e.g., Johnson and Berkley 1999a; Raesly 2001; Bischof
2003; Pitt et al. 2003; Hubbard and Serfass 2004). Since
1976, reintroduction projects have been carried out in 21
American states and one Canadian province, Alberta (Hub-
bard and Serfass 2004).
The habitat requirements of the North American river ot-
ter are well known (e.g., Melquist and Hornocker 1983;
Melquist and Dronkert 1987; Larivie
`re and Walton 1998).
As emphasized by Melquist and Dronkert (1987), two im-
portant habitat characteristics need to be present along rivers
and streams, i.e., access to prey and shelter. As top-level
Received 13 September 2008. Accepted 2 April 2009. Published on the NRC Research Press Web site at cjz.nrc.ca on 30 April 2009.
D. Gallant,1,2 L. Vasseur, and C.H. Be
´rube
´.De
´partement de biologie, Universite
´de Moncton, Moncton, NB E1A 3E9, Canada.
M. Dumond. Nunavut Wildlife Division, Department of Environment, Box 377, Kugluktuk, NU X0B 0E0, Canada.
E. Tremblay.3Kouchibouguac National Park of Canada, Kouchibouguac, NB E4X 2P1, Canada.
1Corresponding author (e-mail: Daniel.Gallant@uqar.qc.ca).
2Present address: De
´partement de biologie, chimie et ge
´ographie, Universite
´du Que
´bec a
`Rimouski, 300 Alle
´e des Ursulines, Rimouski,
QC G5L 3A1, Canada.
3Present address: Associate Vice-President, Research, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada.
422
Can. J. Zool. 87: 422–432 (2009) doi:10.1139/Z09-035 Published by NRC Research Press
predators of freshwater ecosystems, river otters are resource-
ful and prey upon a wide diversity of mostly aquatic verte-
brates (Greer 1955; Bowyer et al. 1994). Consequently, their
distribution or abundance is less likely to be affected by
fluctuations of particular prey species compared with speci-
alized predators such as the lynx (Lynx canadensis Kerr,
1792) (e.g., O’Donoghue et al. 1997). Provided that poten-
tial preys are available in sufficient numbers, the occurrence
of river otters in a region would be ultimately restricted by
their dependence on the availability of adequate shelters.
River otters are semiaquatic and do not possess the phys-
iological adaptations to stay indefinitely in water (Melquist
and Dronkert 1987), thus they depend daily on terrestrial
shelters. River otters rarely create their own burrows
(Johnson and Berkley 1999b), relying instead on pre-existing
refuges such as natural formations (Melquist and Hor-
nocker 1983), burrows dug by other species (Melquist and
Hornocker 1983), mature forests and conifers that offer
good cover along riverbanks (Mowbray et al. 1976;
Newman and Griffin 1994; Bowyer et al. 1995; Swimley
et al. 1998), and beaver (Castor canadensis Kuhl, 1820)
ponds, lodges, and burrows (Melquist and Hornocker
1983; Dubuc et al. 1990; Newman and Griffin 1994; Reid
et al. 1994; Swimley et al. 1998). They have also been as-
sociated with steep banks (Reid et al. 1994; Swimley et al.
1998) and soils of silt or organic matter (Reid et al. 1994).
Reid et al. (1994) hypothesized that steep banks facilitate
the creation of short underwater burrows that possess air-
filled chambers over the water level, whereas soils of silt
or organic matter, which are easier to burrow into, would
tend to contain more burrows than banks composed of
rocks, boulders, gravel, or sand.
It is generally known that disturbances of anthropogenic
origin can have adverse effects on otter populations (Lode
´
1993; Bowyer et al. 1994; Mason 1995; Barbosa et al.
2001; Dean et al. 2002). For the North American river otter,
because most studies dealing with habitat selection by otters
have been conducted in regions with markedly low (e.g.,
Melquist and Hornocker 1983; Dubuc et al. 1990; Reid et
al. 1994; Swimley et al. 1998) or high (e.g., Bowyer et al.
1994, 1995) levels of anthropogenic disturbances, it is not
well known how their distribution and habitat use on a re-
gional scale are affected by varied anthropogenic disturban-
ces. Acquiring species-specific ecological knowledge on
otters in altered landscapes will help improve the effective-
ness of management and conservation activities (Gallant
2007). We also need to understand the influence of protected
areas adjacent to zones with anthropogenic disturbances on
the ecology of species (e.g., Dumond et al. 2001). This is es-
pecially important for protected areas of small size that suf-
fer adverse external effects because of habitat fragmentation
and the presence of human populations near their borders
(Gurd and Nudds 1999; Parks and Harcourt 2002).
We conducted a study to investigate winter habitat use by
river otters in an area having both protected and disturbed
riparian habitats. We applied an information–theoretic ap-
proach by computing Akaike’s information criterion (AIC)
for various models composed of different types and combi-
nations of variables (Anderson and Burnham 2002; Burnham
and Anderson 2002) to compare their performance and rela-
tive importance in describing habitat-use patterns by river
otters as shown by their activity signs.
Barbosa et al. (2001), studying Eurasian otters (Lutra lu-
tra (L., 1758)) on a large geographical scale, found that en-
vironmental factors had more influence on the occurrence of
that otter species than anthropogenic factors. Melquist and
Hornocker (1983) observed that river otters preferred sites
with low levels of human activities, but would occupy more
perturbed sites as long as food and shelter were available.
From these observations, Prenda et al. (2001) proposed that
the importance of the impact of anthropogenic disturbances
on otters is conditioned by the availability of shelter. Based
on results from Barbosa et al. (2001) and casual observa-
tions by Melquist and Hornocker (1983), we first predicted
that models using habitat factors would better describe the
occurrence of river otter activity signs compared with mod-
els based on anthropogenic factors. Secondly, we also pre-
dicted that river otter activity signs in the unprotected
portion of our study area would be less abundant than in
the protected one, which contains more intact riparian habi-
tats. Published studies attest that the occurrence of otters in a
given landscape tends to be negatively correlated to anthro-
pogenic disturbances (Lode
´1993; Bowyer et al. 1995; Bar-
bosa et al. 2001; Robitaille and Laurence 2002), but
positively correlated with habitat characteristics they depend
upon for food and shelter (Newman and Griffin 1994; Reid
et al. 1994; Swimley et al. 1998; Madsen and Prang 2001).
Thirdly, we therefore predicted that models based on a com-
bination of factors representing both habitat and anthropo-
genic features of riparian environments would better explain
occurrence of river otter activity signs compared with mod-
els using factors from only one of those two categories.
Materials and methods
Study area
The study area comprised Kouchibouguac National Park
of Canada (KNPC) and its vicinity (Fig. 1). The Park covers
an area of 238.8 km2, is part of New Brunswick’s lowlands,
and is representative of the Maritime Coastal Plains (De-
sloges 1980). The topography is flat and contains eight ma-
jor watercourses with numerous bogs and swamps: Portage
River, Carrigan Brook, Fontaine River, Black River, Rankin
Brook, Kouchibouguac River, Major Brook, and Kouchibou-
guacis River (Desloges 1980). Except for Portage River, all
other watercourses empty into a lagoon and dune system.
The two main rivers, Kouchibouguac and Kouchibouguacis,
are both tidal. The climate is humid continental with impor-
tant maritime influences near the shore (Graillon et al.
2000). Mean annual temperature is 4.8 8C, mean freeze-free
period is 177 days, and mean annual precipitation is
979 mm (Desloges 1980). The majority of forested areas
are mixed, dominated by balsam fir (Abies balsamea (L.) P.
Mill.) and birch (genus Betula L.), or coniferous with mostly
black spruce (Picea mariana (P. Mill.) B.S.P.) (Graillon et
al. 2000). Speckled alder (Alnus rugosa (Du Roi) Spreng.)
dominates the banks of smaller streams in the area. The
study area also included the 39.5 km2Black River Provin-
cially Protected Zone of New Brunswick (BRPPZNB;
Fig. 1). The rest of the study area consisted of unprotected
zones reaching farther inland along the Portage, Kouchibou-
Gallant et al. 423
Published by NRC Research Press
guac, Kouchibouguacis, and St-Charles rivers (Fig. 1). The
unprotected portion of the study area was at various stages
of succession, with low-density residential areas, agricultural
lands, and regions with undisturbed forested riverbanks.
Snowmobile traffic was prominent on the Kouchibouguacis
River both in protected and unprotected zones, whereas all
other rivers had little or no snowmobile traffic. In the unpro-
tected portion of our study area, otter-trapping effort was
low and occasional. One person trapped otters in the region
adjacent to our study area in 2002 only, and one of the ot-
ters caught was located at the limit of our study area on the
St-Charles River. Otter trapping was not known to occur in
or near our study area in subsequent years.
Sampling protocol
We documented river otter activity signs from early Janu-
ary until the end of April 2003 and 2004 by conducting
transects along the shores of the six main rivers of the study
area (Fig. 1), as well as tributary streams associated with
them. Detection of fresh activity signs is higher in winter
because of the conspicuous, corridor-like tracks that each
animal leaves in the snow, linking all other activity signs to
them. The homogeneous substrate left by recurrent snowfalls
in winter also safeguards against possible biases linked to
differential detection rates that can occur on the landscape
in other seasons (Conroy and French 1987; Romanowski et
al. 1996).
We conducted transects after >12 h waiting periods fol-
lowing appreciable snowfalls (i.e., >2 cm), thereby leaving
time for otters to manifest their presence and produce activ-
ity signs on the fresh snow. We used light snowmobiles
when river width and ice thickness made it possible and
snowshoes otherwise. We searched shores as two riders on
separate machines, riding single file at slow speed (i.e., 5–
10 km/h) along one shore after the other on the given river,
and stopping at will to inspect and document all potential
river otter activity signs found (i.e., snow tracks, faeces, bur-
rows, water access holes, and direct sightings). We sampled
rivers after each snowfall in random order and alternated the
order for ensuing snowfalls. We maintained sampling efforts
up to 6 days after each snowfall and waited for another
snowfall to cover aging multilayered tracks before continu-
ing the survey.
We conducted continuous transects, meaning that regard-
less of means of transport, 1 or 2 days were invested in
scrutinizing the chosen river (i.e., full length of respective
rivers within the study area). This maximized our ability to
document river otter habitat use. We sampled the study area
(Fig. 1) with riparian transects three times during the winter
of 2003, amounting to 769 km of riverbank inspections.
During the winter of 2004, we sampled the same area one
time, with 239 km of riverbank inspections. We were able
to conduct more transects in 2003 because snow precipita-
tions were frequent and ice conditions were stable for a lon-
ger period than in 2004. The study area represented
approximately 131 km of riverbanks in the protected areas
of KNPC and BRPPZNB, and 146 km in the unprotected
areas, both shores of sampled rivers considered (Fig. 1).
We recorded coordinates (UTM, Grid #20, in metres, Gar-
min12 XL global positioning system), date, and time for the
beginning and end of each transect, as well as for all sites
where otter activity signs were found. At each otter activity
site, we documented the types of activity signs found and a
variety of habitat factors (within a 20 m radius) known from
literature to be relevant to the ecology of river otters
(Table 1; see references cited in Introduction). We recorded
anthropogenic activities present at otter activity sites when
they were within 100 m of given sites (Table 1). We docu-
mented studied habitat and anthropogenic factors as binary
or categorical–ordinal variables by estimating them on loca-
tion. To study what otters selected in the study area as a
function of what was available and to assess habitat differ-
ences between protected and unprotected zones, we also
documented the same variables (Table 1) at independently
Fig. 1. Extent of the study area in New Brunswick, Canada, which comprises Kouchibouguac National Park of Canada, the Black River
Provincially Protected Zone of New Brunswick, and unprotected areas in the vicinity. Rivers sampled were (1) Portage, (2) Fontaine,
(3) Black, (4) Kouchibouguac, (5) Kouchibouguacis, and (6) St-Charles.
424 Can. J. Zool. Vol. 87, 2009
Published by NRC Research Press
established sites designated as habitat stations. We deter-
mined their position in advance on topographical maps, at
500 m intervals along both shores of rivers and streams
sampled during the winter surveys. The total number of hab-
itat stations documented amounted to 251 in KNPC, 20 in
BRPPZNB, and 295 in the unprotected portion of the study
area.
Because of logistics, we completed the measurement of
habitat and anthropogenic factors during the summers of
2003 and 2004 for all habitat stations and locations with ac-
tivity signs. We cross-checked data on anthropogenic distur-
bances with topographic maps and aerial photographs. We
did not consider hiking trails as disturbances because they
were discrete and infrequently used. We did not consider
abandoned fields as current disturbances when categorizing
sites as having or lacking anthropogenic disturbances be-
cause they have been left untouched since the creation of
the park in 1969 and patchily reverted to forests or bush-
dominated parcels.
Data analysis
We created a binary response variable, with sites of activ-
ity signs coded as ‘‘1’’ and habitat stations as ‘‘0’’. Because
our data consisted of binary and ordinal explanatory varia-
bles with a binary response variable, we used logistic regres-
sion procedures in SPSS1for Windows version 8.0 (SPSS
Inc. 1997) to analyse the relationships between habitat and
anthropogenic factors and the dependent response variable.
The four sweeps of the study area we accomplished in
search of activity signs constitute replication of samples,
not replication of treatment (Hurlbert 1984). Consequently,
we considered each survey as a distinct mensurative experi-
ment and analysed the four data sets separately. We used
Pearson’s correlations and Yule’s coefficient of association
to ensure that no multicollinearity problems existed among
explanatory variables (criterion used for problematic correla-
tions was >0.7; Parra et al. 2004; Santiago-Alarcon and
Parker 2007; Szor et al. 2008). We used an information–
theoretic approach to determine what were the important
features of riparian habitats that influenced river otter hab-
itat use in a study area having two contrasting regions
(protected and unprotected). We compared the performance
of different models, constituting various assemblages of
predictor variables, by computing AICc(AIC corrected for
small-sample bias) values for each of them (Burnham and
Anderson 2002). We tested for spatial autocorrelation for
each predictor variable using Geary’s Cstatistic computed
by Monte Carlo simulations in R version 2.8.1 with the
package SPDEP (R Development Core Team 2008).
Geary’s Cranges from 0 to 2, with values near 1 repre-
senting random distribution, values near 0 representing
clustering of similar values (i.e., strong spatial autocorrela-
tion), and scores near 2 representing clustering of dissimi-
lar values (Geary 1954).
For each of the four winter surveys of otter activity in the
study area, we compared seven different models using AICc.
The models consisted of a priori chosen combinations of the
variables we measured at habitat stations and sites found
with otter activity signs. We used logistical regressions and
entered designated predictor variables in a single step for
each model. The models were built to explore the relative
importance and relevance of different categories of habitat
features for explaining river otter occurrence and habitat
use. We describe here candidate variables for the various
models, provided they satisfied our screening criteria for
multicollinearity and spatial autocorrelation problems. The
Table 1. Variables documented at 566 habitat stations and 266 sites with river otter (Lontra canadensis) activity signs detected during
winter riparian transect surveys conducted in 2003 and 2004 in Kouchibouguac National Park of Canada and surrounding areas.
Factor
abbreviation Factor description and values
Variable
type
DOMVG Dominant vegetation at site: bare soil (1), grass (2), shrubs (3), deciduous forest (4), mixed forest (5), coniferous
forest (6)
Ordinal
SUCST Successional stage of dominant vegetation: nonexistent (0), young (1), intermediate (2), mature (3) Ordinal
CANOP* Canopy closure at site: 0%–25% (1), 25%–50% (2), 50%–75% (3), 75%–100% (4) Ordinal
UDENS Understory density at site: absent (1), sparse (2), dense (3) Ordinal
OVEG Overhanging vegetation at site: none (1), scarce (2), abundant (3) Ordinal
RIWTH River width at site: 0–1 m (1), 1–5 m (2), 5–10 m (3), 10–25 m (4), 25–50 m (5), 50–100 m (6), >100 m (7) Ordinal
TRIBUT Tributary streams in the vicinity: presence (1), absence (0) Binary
SLOPE Slope of the bank at site: 08(0), weak 108(1), considerable 458(2), steep 758(3), abrupt 908(4) Ordinal
UDCUT Undercut bank at site: presence (1), absence (0) Binary
SOIL Type of soil at site: rocks–gravel–sand (1), silt – organic matter (2), mixed (1.5) Ordinal
DEBRIS Ground debris at site: absent (1), rare (2), abundant (3), highly abundant (4) Ordinal
BPOND Beaver pond in the vicinity: presence (1), absence (0) Binary
LOGNG Logging within 100 m of site: presence (1), absence (0) Binary
FIELD Fields within 100 m of site: presence (1), absence (0) Binary
OFIELD Abandoned fields within 100 m of site: presence (1), absence (0) Binary
CAMPS Camps, cottages, or camping grounds within 100 m of site: presence (1), absence (0) Binary
BLDNG Houses and other buildings within 100 m of site: presence (1), absence (0) Binary
DROAD Dirt road within 100 m of site: presence (1), absence (0) Binary
PROAD Paved road within 100 m of site: presence (1), absence (0) Binary
HIWAY Highway within 100 m of site: presence (1), absence (0) Binary
OTHER Other uncategorized anthropogenic disturbances within 100 m of site: presence (1), absence (0) Binary
*Because this is a winter study, the canopy closure estimations were based on conifers only.
Gallant et al. 425
Published by NRC Research Press
TOTAL model considered all 18 variables measured in the
field (for all variables and their abbreviations see Table 1),
while the HABITAT model considered all habitat-related
variables, without those related to anthropogenic disturban-
ces (DOMVG, SUCST, CANOP, UDENS, OVEG, RIWTH,
TRIBUT, SLOPE, UDCUT, SOIL, DEBRIS, BPOND). The
VEGETATION model exclusively considered vegetation-
related predictor variables (DOMVG, SUCST, CANOP,
UDENS, OVEG) and the WATER model only considered
those related to hydrology (RIWTH, TRIBUT, BPOND).
The SUBSTRATE model considered variables describing
ground characteristics along riverbanks (SLOPE, UDCUT,
SOIL, DEBRIS). The ANTHROPOGENIC model consid-
ered variables describing human disturbances (FIELD,
CAMPS, BLDNG, DROAD, PROAD, OTHER). The sev-
enth model, called COMBINED, varied from one survey
data set to the other because it was composed of the best
variable of each category (i.e., VEGETATION, WATER,
SUBSTRATE, ANTHROPOGENIC). Separately, for each
of the four survey data sets, we used Wald’s statistic to
judge which variable was the best predictor variable within
each category of variables. We made those comparisons by
analysing each variable separately, using logistical regres-
sion analysis.
Results
Habitat differences in protected versus unprotected areas
Anthropogenic disturbances in the unprotected portion of
the study area (present at 60.7% of 295 habitat stations)
were more abundant than in the protected zones of KNPC
and BRPPZNB (present at 14.7% of 271 habitat stations;
Fig. 2). The majority of these disturbances in the unpro-
tected zone consisted of fields (FIELD, 33.9%), houses and
other buildings (BLDNG, 29.5%), and paved roads
(PROAD, 20.3%; Fig. 2). Within the protected areas, the
few occurrences of anthropogenic disturbances mostly con-
sisted of paved roads (PROAD, 8.5%), dirt roads and ski or
cycling trails (DROAD, 8.1%), and abandoned field sites
(OFIELD, 7.7%; Fig. 2), the latter which we did not con-
sider as current disturbances. In the unprotected zone
(9.2%) and in protected areas (3.7%), additional disturban-
ces (OTHER factor) included a few small floating wharves,
two small commercial fishing wharves, small fixed fishing
nets and cabins used in winter, large electricity lines cross-
ing rivers, parking lots, active cemeteries, and gravel pits.
We excluded from further analyses the two rarest anthropo-
genic disturbances recorded in our study area, i.e., logging
(LOGNG) and highways (HIWAY; Fig. 2).
Riverbanks in the protected areas had more forests
(DOMVG; Fig. 3a), dense underwood (UDENS; Fig. 3d),
organic matter or silt-dominated soils (SOIL; Fig. 3j),
ground debris (DEBRIS; Fig. 3k) and beaver ponds
(BPOND; Fig. 3l) than the unprotected area. River charac-
teristics were also different, as more tributary streams
(TRIBUT; Fig. 3g) and wider river stretches (RIWTH;
Fig. 3f) were in the protected areas. On the other hand, the
unprotected zone tended to have more sites with overhang-
ing vegetation (OVEG; Fig. 3e) and banks with steeper
slopes (SLOPE; Fig. 3h). Succession stage of vegetation
(SUCST; Fig. 3b), canopy closure (CANOP; Fig. 3c), and
undercut banks (UDCUT; Fig. 3i) were similar for protected
and unprotected zones.
Three pairs of anthropogenic features showed a high de-
gree of correlation (Yule’s coefficient of association >0.8).
They were buildings and fields, buildings and paved roads,
and buildings and the OTHER variable. The BLDNG varia-
ble was the problematic one and we thus excluded it from
the regression analyses done for the descriptive models. All
other pairings of predictor variables meant to be analysed by
logistical regressions were under our >0.7 exclusion crite-
rion. Buildings remain indirectly represented through the
other anthropogenic variables with which it was strongly cor-
related. The BLDNG variable was still considered like other
variables when choosing the best performing anthropogenic
Fig. 2. Frequency of occurrence (%) of anthropogenic attributes at 271 habitat stations sampled in the protected areas of Kouchibouguac
National Park of Canada and the Black River Provincially Protected Zone of New Brunswick, as well as at 295 habitat stations sampled in
the unprotected vicinity.
426 Can. J. Zool. Vol. 87, 2009
Published by NRC Research Press
Fig. 3. Distribution of categorical habitat values expressed as percentages of 271 habitat stations sampled in the protected areas of Kouchi-
bouguac National Park of Canada and the Black River Provincially Protected Zone of New Brunswick, as well as percentages of 295 habitat
stations sampled in the unprotected vicinity.
Gallant et al. 427
Published by NRC Research Press
variable for the COMBINED models. One variable,
RIWTH, had strong spatial autocorrelation (Geary’s C=
0.151). River width in the study area gradually and consis-
tently increased from west to east, resulting in high spatial
autocorrelation (Geary’s C= 0.151). We therefore excluded
RIWTH from regression analyses. Most other predictor vari-
ables had low spatial autocorrelation (Geary’s Cfrom 0.7 to
0.9; CANOP, BPOND, CAMPS, DEBRIS, DROAD,
DOMVG, UDCUT, OTHER, PROAD, SLOPE, SOIL, TRI-
BUT, UDENS, SUCST), but a few had moderate scores
(Geary’s Cfrom 0.5 to 0.6; FIELD, BLDNG, OVEG).
Those with moderate autocorrelation tended to have values
occurring in patches, but they occurred at various places in
the study area and would not be problematic.
Occurrence of activity signs in protected and
unprotected areas
In total, 266 locations with river otter activity signs were
recorded (Fig. 4a). For similar lengths of riverbanks
searched inside and outside the protected areas (Fig. 4b),
the abundance of sites with activity signs differed drastically
between the two regions. The majority of them (n= 258)
were in the protected areas (Fig. 4a). River otter activity
signs were found in all six major river systems sampled in
KNPC, including along the north shore of St-Charles River,
which constitutes the southern border of the park (Fig. 1).
Activity signs were also found along Black River in the
BRPPZNB (Fig. 1). Only eight activity signs were found at
four locations in the unprotected zone (Fig. 4a). They were
located along Portage River, which is undisturbed, and in a
relatively undisturbed region of the Kouchibouguac River,
7.9 km from the nearest KNPC border (Fig. 1). Some were
also found in proximity to the park on MacKay’s Brook,
which empties into Black River.
Distribution of river otter activity signs
Logistical regressions applied to individual predictor vari-
ables showed that those representing anthropogenic distur-
bances were negatively correlated with the binary
dependent variable (i.e., occurrence of otter activity signs),
while variables describing the different habitat features
were mostly positively correlated with the dependent varia-
ble. The only exceptions (negative but not statistically sig-
nificant correlations) were SLOPE (p= 0.960) and UDCUT
(p= 0.946) in the second survey of 2003. We obtained con-
sistent patterns when comparing the seven different models
within the four data sets. For all the data sets, the best mod-
els were those that included a mix of the different categories
of variables, as shown by the smallest AICcand Divalues
(Table 2). For the first and second data sets, the COM-
BINED model was the best model describing the occurrence
of otter activity signs; for the third and fourth data sets, the
TOTAL model was the best one, despite being penalized in
the AICcstatistic for the large number of parameters (varia-
bles) that they included. Consistently, the HABITAT model
was better than the ANTHROPOGENIC model at explaining
variability in the data. The HABITAT model consistently
had the third best performance for all four data sets.
Since the four models constituted mutually exclusive sets
of variables (i.e., VEGETATION, WATER, SUBSTRATE,
ANTHROPOGENIC), the WATER model had the best per-
formance for the first, second, and third data sets (smallest
AICc), but the SUBSTRATE model was the best one for
the fourth data set (Table 2). Some factors had more impor-
tant impacts than others in the results. Beaver ponds
(BPOND) were consistently selected in the COMBINED
models, which was composed of the best predictor variable
within each of the four categories of variables. This variable
was responsible for the good performance of the WATER
model when compared with the VEGETATION, SUB-
STRATE, and ANTHROPOGENIC models. Fields (FIELD)
was the most important anthropogenic variable and was con-
sistently selected in the COMBINED models (Table 2).
Generally, habitat features were more important than anthro-
pogenic disturbances in explaining the occurrence of signs
of otter activity, but models that also incorporated variables
describing anthropogenic disturbances (TOTAL and COM-
Fig. 4. Number of (a) sites with river otter (Lontra canadensis) ac-
tivity signs and (b) habitat stations spanning the riverbanks
searched for four surveys conducted in the study area that consists
of Kouchibouguac National Park of Canada, the Black River Pro-
vincially Protected Zone of New Brunswick, and the unprotected
surrounding area. Survey periods are from 15 to 29 January 2003
for survey 1, 30 January to 2 March 2003 for survey 2, 27 February
to 11 April 2003 for survey 3, and 10 February to 23 March 2004
for survey 4.
428 Can. J. Zool. Vol. 87, 2009
Published by NRC Research Press
BINED models) were the best ones by a large margin, as in-
dicated by the high wivalues (Table 2).
Discussion
Our results conform to our predictions and echo those of
Barbosa et al. (2001) for the Eurasian otter, which showed
that environmental factors had more influence on otter pres-
ence than anthropogenic ones. Despite our finding that hab-
itat features were more important than anthropogenic ones,
the best of the studied models for describing occurrence of
otter activity signs were those which included both habitat
and anthropogenic factors, hence confirming our second pre-
diction. This precludes us from concluding that anthropo-
genic disturbances did not have a considerable effect on
river otters. As predicted, most otter activity sites were
found in the protected areas where disturbance was less
than the unprotected part of our study area. However, our
data suggest that it is not the presence of a given anthropo-
genic structure that affects distribution of river otters the
most, but rather how anthropogenic activities and structures
lead to the loss of particular habitat features (e.g., beaver
ponds) and, consequently, the loss of those constituents of
habitat quality relevant to river otters’ habitat requirements.
Our study design and analyses cannot separate the effects of
the presence of an anthropogenic activity and the loss of
habitat features important to otters. However, the fact that
the unprotected portion of our study area had a higher oc-
currence of anthropogenic features (Fig. 2) but fewer of the
habitat features known to be used by otter (Fig. 3), and that
there was a dominating importance of habitat variables rela-
tive to anthropogenic ones (Table 2), support our above-
Table 2. Model comparisons based on comparisons of Akaike’s information criterion corrected for small-sample bias (AICc) values com-
puted for seven different models fitted by logistic regressions for each of four separate surveys documenting habitat use by river otters
(Lontra canadensis) in Kouchibouguac National Park of Canada and surrounding areas during the winters of 2003 and 2004.
Survey period Model
Model
ID. –2(loglikelihood)
Number of
parameters
(K)* AICc
DAICc
(Di)
Akaike
weight
(wi)
Sample
size (n)
15–29 January 2003 TOTAL{1 120.80 17 156.34 17.44 0.00 416
HABITAT{2 129.96 12 154.73 15.84 0.00 416
VEGETATION§3 146.73 6 158.94 20.04 0.00 416
WATER|| 4 142.35 3 148.41 9.51 0.01 416
SUBSTRATE}5 151.80 5 161.95 23.05 0.00 416
ANTHROPOGENIC** 6 147.46 6 159.67 20.77 0.00 416
COMBINED{{ 7 128.75 5 138.90 0.00 0.99 416
30 January to 2 March 2003 TOTAL 1 206.90 17 242.06 9.68 0.01 546
HABITAT 2 218.69 12 243.28 10.89 0.00 546
VEGETATION 3 298.65 6 310.81 78.42 0.00 546
WATER 4 247.23 3 253.27 20.89 0.00 546
SUBSTRATE 5 273.92 5 284.03 51.65 0.00 546
ANTHROPOGENIC 6 297.82 6 309.98 77.59 0.00 546
COMBINED{{ 7 222.27 5 232.38 0.00 0.99 546
27 February to 11 April 2003 TOTAL 1 431.18 17 466.15 0.00 0.97 647
HABITAT 2 450.34 12 474.83 8.68 0.01 647
VEGETATION 3 507.44 6 519.57 53.42 0.00 647
WATER 4 491.17 3 497.21 31.05 0.00 647
SUBSTRATE 5 491.08 5 501.17 35.02 0.00 647
ANTHROPOGENIC 6 506.44 6 518.57 52.42 0.00 647
COMBINED§§ 7 464.59 5 474.68 8.53 0.01 647
10 February to 23 March 2004 TOTAL 1 359.01 17 394.14 0.00 1.00 558
HABITAT 2 390.82 12 415.39 21.25 0.00 558
VEGETATION 3 459.44 6 471.59 77.45 0.00 558
WATER 4 505.29 3 511.33 117.19 0.00 558
SUBSTRATE 5 438.86 5 448.97 54.83 0.00 558
ANTHROPOGENIC 6 482.06 6 494.21 100.07 0.00 558
COMBINED|||| 7 396.97 5 407.08 12.94 0.00 558
*Includes +1 to account for the intercept.
{Predictor variables: DOMVG, SUCST, CANOP, UDENS, OVEG, TRIBUT, SLOPE, UDCUT, SOIL, DEBRIS, BPOND, FIELD, CAMPS, DROAD,
PROAD, OTHER.
{Predictor variables: DOMVG, SUCST, CANOP, UDENS, OVEG, TRIBUT, SLOPE, UDCUT, SOIL, DEBRIS, BPOND.
§Predictor variables: DOMVG, SUCST, CANOP, UDENS, OVEG.
||Predictor variables: TRIBUT, BPOND.
}Predictor variables: SLOPE, UDCUT, SOIL, DEBRIS.
**Predictor variables: FIELD, CAMPS, DROAD, PROAD, OTHER.
{{Predictor variables: SUCST, BPOND, SOIL, FIELD.
{{Predictor variables: CANOP, BPOND, SOIL, FIELD.
§§Predictor variables: DOMVG, BPOND, DEBRIS, FIELD.
||||Predictor variables: OVEG, BPOND, DEBRIS, FIELD.
Gallant et al. 429
Published by NRC Research Press
stated conclusion. For our two-winter study, the distribution
pattern of river otter activity signs was very similar to that
of a pilot study done in the same region, where only 6 of
115 and 7 of 255 activity signs found during the winters of
2000 and 2001, respectively, were outside the protected
areas of KNPC and BRPPZNB (M. Dumond and C.H. Be
´rube
´,
unpublished material).
Conversely, our results showing the predominant effect of
habitat features also indicate that river otter presence in ri-
parian habitats is not completely incompatible with the
anthropogenic activities. This is in accordance with Barbosa
et al. (2001) and Melquist and Hornocker (1983), as well as
Mech (2003) who found signs of river otter activity in an
urbanized area, and Macdonald and Mason (1982) who re-
ported Eurasian otter activity signs in abundance at locations
with considerable levels of anthropogenic disturbances. In
Maryland, Mowbray et al. (1976) also observed river otters
in residential areas where needed habitat features were
present. Our results and these examples indicate that it is
not the presence of anthropogenic activities per se but the
degree of changes to riparian habitats that is important. One
practical implication of this is that river otter occurrence
acts primarily as an indicator of features attesting to certain
aspects of the health and integrity of riparian habitats, rather
than as a negative indicator of the presence of particular
anthropogenic activities. The species is not completely in-
compatible with the presence of human activities and will
rather respond to the damage or changes that disturbances
bring to riparian habitats. This is a valuable characteristic
for potential indicators of ecological integrity. To this effect,
the anthropogenic factor most correlated (negatively) with
the occurrence of otter activity signs was fields, as reflected
in our results for the COMBINED models. Fields offer no
tree cover, while river otters usually select locations having
good vegetative cover (Mowbray et al. 1976; Newman and
Griffin 1994; Bowyer et al. 1995; Swimley et al. 1998). In
the unprotected part of our study area mostly, fields and
lawns typically extended all the way to the edge of the
watercourse or a few metres from it. Fields constituted the
most drastic and widespread habitat alteration in our study
area.
Beaver ponds were an important habitat feature that river
otters used and this was reflected in our model comparisons.
Beavers modify riparian habitats considerably (Naiman et al.
1988; Wright et al. 2002; Bailey et al. 2004; Rosell et al.
2005) and create lodges and underwater burrows, which are
known to be used by river otters (Melquist and Hornocker
1983; Reid 1984). The ponds they create can provide favor-
able habitat for some of the fish species that could constitute
potential preys for otters (Gard 1961; Alexander 1998;
Snodgrass and Meffe 1998; Schlosser and Kallemeyn 2000).
In the literature, beaver ponds constitute one of the habitat
features most often reported to be used by river otters (e.g.,
Green 1932; Greer 1955; Melquist and Hornocker 1983;
Reid 1984; Dubuc et al. 1990; Newman and Griffin 1994;
Reid et al. 1994; Swimley et al. 1998). Despite the great im-
portance of beaver ponds as a habitat characteristic used by
otters, our results show that a variety of habitat features are
important to river otters. This is in accordance with a
summer study done by LeBlanc et al. (2007) within Kouchi-
bouguac National Park of Canada, which showed that
although river otter activity at beaver ponds was concen-
trated at ponds inhabited by beavers, other features of bea-
ver ponds, like size of the water impoundment and
vegetation cover at the water’s edge, played a significant
role in explaining why some beaver ponds were often visited
by otters, while others were not. Beaver ponds were rare
outside the protected zones of our study area. This is another
case of habitat alteration by humans, with beavers in devel-
oped areas generally considered nuisance animals to be
taken charge of, because of the damage they can cause on
infrastructure (e.g., Bhat et al. 1993; Jensen et al. 2001).
Our study contributes information about how common
and varied anthropogenic disturbances (i.e., fields, houses,
roads, and others) in regions having both protected and dis-
turbed areas affect river otter distribution and habitat use in
riparian habitats. We focused on the effect of a variety of
factors other than that of water quality, the latter being a
popular topic for river otter research in a management or
conservation context (e.g., Mierle et al. 2000; Taylor et al.
2000; Ben-David et al. 2001). In regions where water pollu-
tion is an issue, river otters might be absent even if river-
banks appear undisturbed and suitable. Although this was
not an issue in our study area, managers should consider
water quality when monitoring the distribution of river otter
activity signs. Moreover, our study was conducted in a pro-
ductive estuarine region where prey accessibility is unlikely
to be an issue. However, prey richness was probably lower
inland, in the upstream portions of rivers, but river otter ac-
tivity signs were still found there where unaltered riverbanks
had favorable habitat features. River otters are resourceful as
predators and are able to find prey even after ecological dis-
asters that diminish prey diversity and abundance (Bowyer
et al. 1994). It is difficult to measure prey availability to a
specific predator, but like water quality, this factor should
be considered if interpreting the occurrence of activity signs
in a monitoring context because it potentially has a major
influence on otter populations (Kruuk et al. 1991; Ruiz-
Olmo et al. 2001).
Acknowledgements
We thank park staff at KNPC for significant and sustained
logistical support for the duration of the study. We are in-
debted to S. Martinez, B. Peters, P. Roguet, G. Daigle, S.
Pouzet, and M. Gallant for their field assistance. Funding
was provided by the New Brunswick Wildlife Trust Fund
(C.H. Be
´rube
´), the Faculte
´des e
´tudes supe
´rieures et de la
recherche of the Universite
´de Moncton with Canadian Her-
itage Scholarships (D. Gallant), the K.C. Irving Chair in
Sustainable Development (L. Vasseur), and KNPC. We
thank J.-F. Robitaille, M.-A. Villard, S. Reebs, and D.G.
Kehler for helpful suggestions that they made on an earlier
draft of the manuscript.
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... This results in the transport of nutrients from the marine environment to the coastal terrestrial community (Ben-David et al. 1998) which has a significant influence on the vegetation community, both through nutrient enrichment and disturbance by river otters (Roe et al. 2010). River otters have also been identified as an indicator of sustainable forest management (Beazley and Cardinal 2004) and their occurrence acts primarily as an indicator of features attesting to certain aspects of the health and integrity of coastal and riparian habitats (Gallant et al. 2009). ...
... Shrubs.-Increasing percentage cover of understory shrubs was 1 of the most important habitat characteristics explaining differences between used (latrine) and available (random) sites in Prince William Sound (Bowyer et al. 1995). Gallant et al. (2009) reported that occurrence of river otters increased as density of the understory increased. However, Crowley et al. (2012) observed that shrub cover (0-2 m) had a negative influence on the number of scats at latrine sites, although this finding was not statistically significant. ...
... River otters rarely create their own burrows (Johnson and Berkley 1999), relying instead on pre-existing refuges such as down wood (Bunnell and Houde 2010). Gallant et al. (2009) observed that occurrence of river otters increased as abundance of down wood increased. Woolington (1984) described an association between natal dens in southeast Alaska and down wood. ...
Full-text available
Technical Report
The Tongass National Forest in southeast Alaska previously relied on timber volume, a measure related to timber production and economics, to provide information on forest structure, ecosystem diversity, and wildlife habitat. The Forest Service developed a measure (Size Density Model [SDM]) based on tree density and mean tree diameter as a more comprehensive assessment of these key characteristics. To fully incorporate the SDM into planning and management of wildlife habitat and populations, information was needed on the relationship of land cover classes described by the SDM and habitat for wildlife species of conservation concern.
... Exurban development, characterized as residential land outside of urban-suburban areas in which parcels are generally too small to be considered productive agricultural land, has increased even more rapidly (Theobald 2005). Human habitat modification often leads to habitat loss and fragmentation in both urban and rural areas (Gallant et al. 2009;Cianfrani et al. 2013;Gray et al. 2016). When severe enough, isolation and conversion of habitat for human use can ultimately lead to extirpation (Noss et al. 1996;Magle et al. 2010). ...
... Strong selection of herbaceous wetlands by river otters in the Midwest is observed commonly and thought to be influenced by prey availability (Helon 2006;Wilson 2012). Aside from aquatic habitat, selection of woodland cover as opposed to open agricultural fields, grasslands (LeBlanc et al. 2007;Gallant et al. 2009;Jeffress et al. 2011), or developed areas (Holland 2016) is often reported from sign surveys. ...
... Within our study area, Crab Orchard National Wildlife Refuge (CONWR; 37°43′10″N, 89°1′16″W) represented a rural site of minimal human disturbance surrounded by varying levels of land development. CONWR (184 km 2 ) is located in Williamson, Jackson, and Union Counties, Illinois and is managed by the U.S. Fish and Wildlife Service (Frisk 2007). The area surrounding CONWR was composed of a matrix of agricultural fields and exurban development along Highway 13, with one micropolitan area (Carbondale, 591 persons/km 2 -U.S. Census Bureau 2010a, 2011) located 4.6 km to the west and another micropolitan area (Herrin-Marion, 492 persons/km 2 ) 3.5 km to the northeast (U.S. Census Bureau 2010bBureau , 2010cBureau , 2011. ...
Article
River otter populations have expanded across much of their historical range, including in Illinois where they were reintroduced from 1994 to 1997. These expanding populations are recolonizing a wide range of landscapes with different levels of human modification, which could influence how river otters use space in relation to habitat characteristics and each other. Our objectives were to quantify 1) home ranges and core areas, 2) sociality, and 3) habitat selection across all available habitats and within home ranges (second- and third-order selection, respectively) of 22 radiomarked river otters (Lontra canadensis) in southern Illinois during 2014–2016. Our study area contained a diverse mix of forest, agriculture, aquatic and wetland habitats, and a range of urban development intensity. We examined sociality using the frequency at which individuals were located < 25 m from a conspecific and compared home-range overlap among individuals based on sex. Habitat selection at the second and third order was analyzed using an eigen-analysis of selection ratios based on landcover categories. Similar to other studies, male river otters had > 2-fold larger home ranges and core areas than females in southern Illinois. Several lines of evidence indicated males were more social than females. Males were located close to a conspecific more frequently than were females, and overlap of home ranges and core areas among males was greater than it was among females or between sexes. As observed in other landscapes, river otters strongly selected herbaceous and wooded wetlands at both second- and third-order scales. River otters selected terrestrial cover types with vegetative cover potentially due to shelter or prey availability. Forests were selected over crop fields at the third-order scale, which was consistent with studies using sign surveys. River otters in our study had home ranges containing 0–40% developed land cover, but we found no evidence that otters living in more developed areas used their home ranges more selectively. River otters in this landscape were plastic in regard to social behavior and habitat selection, highlighting their generalist nature and providing insight into their ability to successfully recolonize areas of the Midwest with sufficient vegetative cover and aquatic habitat, among other factors.
... River otters select for locations with high vegetative cover, often influencing occurrence and distribution (Jenkins and Burrow 1980, LeBlanc et al. 2007, Gallant et al. 2009). Considering this species is less agile on land, vegetation can provide cover for access to reproductive dens, travel to different water sources, and protection from predators (Jenkins and Burrows 1980, Melquist and Hornocker 1983, Reid et al. 1994, LeBlanc et al. 2007). ...
... As the Platte River is a braided river with historically highly variable water levels, river otters may abandon these braided areas during high flows in the reproductive season due to a suspected lack of secluded dens (O'Brien and Currier 1987, Dronkert-Egnew 1991, Horn et al. 2012. Interestingly, research indicates that river otter site use increases with beaver activity, due in part to the influence beavers have on wetland systems by increasing ponding (LeBlanc et al. 2007, Gallant et al. 2009). Artificial sand and gravel development may artificially mimic this process. ...
Article
River otters (Lontra canadensis) encompass a broad geographic range including coastal, riverine, and lacustrine systems. However, knowledge of reproductive behavior and structural den characteristics remain relatively few in the literature, particularly in the Great Plains. Distinctions between the terms “den”, “den site”, “natal den”, and “maternal den” are often ambiguous, obscuring our understanding of river otter’s young-rearing behavior. We used observations and descriptions regarding a single maternal den site and a broad reading of the mustelid literature to propose a more standardized maternal den definition for river otters and specify hypotheses for future research. From 25 April to 13 May 2019 and from 4 April to 30 April 2020, we recorded observations of parental behavior, such as relocation of young to a maternal den and aquatic acclimation, via direct or video surveillance. We also systematically assessed habitat and site characteristics associated with this maternal den. We estimated that the river otter young were relocated to the maternal den between 6 to 8 weeks of age, placing them at 8 to 10 weeks at the time of their first observed aquatic acclimation. The maternal den consisted of a distorted metal pipe (entrance = 9 cm height, 28 cm width) on the bank of an excavated perennial pond within 100 m of multiple anthropogenic structures (i.e. cottage, office), but considerable distance from the Platte River (441 m). The maternal den was located adjacent to a small pond (length = 66.4 m, width = 15.2 m, max depth = 69 cm) on a moderate bank slope (29.5%) in relatively dense herbaceous (x̄ cover = 55.0%, x̄ height = 0.53 m) and woody (x̄ cover = 37.5%, x̄ height = 1.56 m) understory vegetation. We suggest that this unique site may have provided a number of benefits including thermoregulatory advantage, predator protection, relatively stable water depth, and proximate access to resources. We suggest that river otter maternal dens are sites used subsequent to and exclusive of parturition that proceed weaning where females continue to exhibit denning behavior as young are still largely dependent and in the earliest stages of developing motor and survival skills. We hypothesize that a set of interrelated factors distinct to particular juvenile life stages promotes maternal den site selection. This represents the first detailed description of a river otter maternal den and den site reuse in the Central Platte River Valley (CPRV), Nebraska and a rare description from the Great Plains.
... River otters select for locations with high vegetative cover, often influencing occurrence and distribution (Jenkins and Burrow 1980, LeBlanc et al. 2007, Gallant et al. 2009). Considering this species is less agile on land, vegetation can provide cover for access to reproductive dens, travel to different water sources, and protection from predators (Jenkins and Burrows 1980, Melquist and Hornocker 1983, Reid et al. 1994, LeBlanc et al. 2007). ...
... As the Platte River is a braided river with historically highly variable water levels, river otters may abandon these braided areas during high flows in the reproductive season due to a suspected lack of secluded dens (O'Brien and Currier 1987, Dronkert-Egnew 1991, Horn et al. 2012. Interestingly, research indicates that river otter site use increases with beaver activity, due in part to the influence beavers have on wetland systems by increasing ponding (LeBlanc et al. 2007, Gallant et al. 2009). Artificial sand and gravel development may artificially mimic this process. ...
Article
River otters (Lontra canadensis) encompass a broad geographic range including coastal, riverine, and lacustrine systems. However, knowledge of reproductive behavior and structural den characteristics remain relatively few in the literature, particularly in the Great Plains. Distinctions between the terms “den”, “den site”, “natal den”, and “maternal den” are often ambiguous, obscuring our understanding of river otter’s young-rearing behavior. We used observations and descriptions regarding a single maternal den site and a broad reading of the mustelid literature to propose a more standardized maternal den definition for river otters and specify hypotheses for future research. From 25 April to 13 May 2019 and from 4 April to 30 April 2020, we recorded observations of parental behavior, such as relocation of young to a maternal den and aquatic acclimation, via direct or video surveillance. We also systematically assessed habitat and site characteristics associated with this maternal den. We estimated that the river otter young were relocated to the maternal den between 6 to 8 weeks of age, placing them at 8 to 10 weeks at the time of their first observed aquatic acclimation. The maternal den consisted of a distorted metal pipe (entrance = 9 cm height, 28 cm width) on the bank of an excavated perennial pond within 100 m of multiple anthropogenic structures (i.e. cottage, office), but considerable distance from the Platte River (441 m). The maternal den was located adjacent to a small pond (length = 66.4 m, width = 15.2 m, max depth = 69 cm) on a moderate bank slope (29.5%) in relatively dense herbaceous (x̄ cover = 55.0%, x̄ height = 0.53 m) and woody (x̄ cover = 37.5%, x̄ height = 1.56 m) understory vegetation. We suggest that this unique site may have provided a number of benefits including thermoregulatory advantage, predator protection, relatively stable water depth, and proximate access to resources. We suggest that river otter maternal dens are sites used subsequent to and exclusive of parturition that proceed weaning where females continue to exhibit denning behavior as young are still largely dependent and in the earliest stages of developing motor and survival skills. We hypothesize that a set of interrelated factors distinct to particular juvenile life stages promotes maternal den site selection. This represents the first detailed description of a river otter maternal den and den site reuse in the Central Platte River Valley (CPRV), Nebraska and a rare description from the Great Plains. < https://digitalcommons.unl.edu/tnas/526/ >
... Otters can utilise whatever resources available within their habitat due to their opportunistic nature, which has been recorded in terms of prey and habitat availability. Otters commonly respond to the presence of habitat characteristics they use over the presence of anthropogenic structures or activities in an area (Aadrean and Usio, 2017;Gallant et al., 2009;Kamjing et al., 2017;Khoo and Sivasothi, 2018;Shenoy et al., 2003;Theng et al., 2016). Although, not all species of otters have a high resilience towards human-modified landscapes. ...
Article
We determined the occupancy of otter species and assessed several habitat features influencing their occurrence in four different land-use types: continuous logged forests (CF), heavily degraded forest (DF), riparian reserves within oil palm plantation (RR), and oil palm plantations without riparian reserves (OP). Our aim was to ascertain the usefulness of retaining riparian reserve in oil palm dominated landscape for otter conservation. This study was conducted in the Malaysian state of Sabah, northern part of Borneo. We surveyed 36 stream sub-transects across all of the different land-use types and detected otter presence based on their tracks and spraints. Overall, two out of the four otter species found in Sabah were detected within the surveyed areas, i.e., the Asian Small-clawed Otter, A. cinereus and Smooth-coated Otter, L. perspicillata. Streams in agricultural sites were found to have significantly higher otter occupancy compared to forested areas: RR (psi = 0.97), OP (0.83), DF (0.44), and CF (0.37). Using Generalised Linear Modelling (GLM), we identified that otter occupancy in oil palm landscapes was positively influenced by the availability of large trees and other vegetation along the banks. Deeper streams were also more preferred by otters. Interestingly, streams in oil palm plantations located nearer to human settlements recorded higher detection of otter signs. In general, this study suggests that streams in oil palm plantation with riparian vegetation are useful habitat for otter species. Hence, retaining riparian reserves within oil palm plantations is a useful management strategy to improve biodiversity conservation in an agricultural landscape. Citation: Pianzin, A., Wong, A. and Bernard, H. (2021). Riparian Reserves serve as a Critical Refuge for Asian Otters (Aonyx cinereus and Lutrogale perspicillata) in Oil Palm Dominated Landscapes of Sabah, Malaysian Borneo. IUCN Otter Spec. Group Bull. 38 (3): 133-154
... In fact, less structurally-complex habitats, such as scattered restinga shrub formations tend to increase its relative abundance in the landscape for not suffering use conversion. Populations of Leopardus tigrinus and Lontra longicaudis, which are threatened species that occur in the area (IUCN, 2016), are affected by habitat loss in the dense restinga because they are sensitive to human presence and dependent on large areas of preserved forest (Galant, Vasseur Drumond, Tremblay, & Bérubé, 2009;Lyra-Jorge, Ribeiro, Ciocheti, Tambosi, & Pivello, 2010;Nagy-Reis, Nichols, Chiarello, Ribeiro, & Setz, 2017;Triglia, Gómez, Cassini, & Túnez, 2016). Therefore, conservation actions aiming at improving landscape structure in the LNMP should focus on increasing restinga forest habitats in the landscape, maintenance of gallery forests, and gradual recolonization of human populations outside the LMNP area. ...
... North American river otters live along the Atlantic and Pacific coasts of higher latitudes of North America as well as in the northern interior of the continent in Canada and almost all of the USA except the arid southwest (Johnson, 2000;Larivière & Walton, 1998). This widespread species inhabits rivers, marshes, estuaries, and coastal environments (Gallant, Vasseur, Dumond, Tremblay, & Bérubé, 2009;Guertin, Harestad, & Elliott, 2009;Johnson, 2000;Larivière & Walton, 1998;Scordino, Gearin, Riemer, & Iwamoto, 2016). North American river otters are considered to be a more gregarious species than other otters (Kruuk, 2006). ...
Article
We investigated the ability of North American river otters (Lontra canadensis) to visually discriminate between 2D objects. The otters learned to discriminate between stimuli using multiple visual features and then were tested with stimuli in which one of the features was eliminated (color or shape). Two adult otters were trained in a two-alternative forced choice task to discriminate between a red circle and a blue triangle. Test sessions included probe trials containing novel shapes, colors, or shape-color combinations. Both otters successfully learned to discriminate between stimuli varying in multiple features. One of the otters was able to successfully discriminate between novel test stimuli when either color or shape were eliminated as salient features. This study was the first to explore the ability of L. canadensis to use different visual features to recognize objects and provides some preliminary evidence for color vision in this species. This research adds to the sparse literature on perceptual and cognitive capabilities in otters and can be used to support future conservation efforts for this species.
Full-text available
Article
Otter species are known to fluctuate intraspecifically from a solitary lifestyle to group-living arrangements. By examining what is known about habitat use and foraging style in otters of 13 different species, based on 93 studied sites, we assessed (1) the relationship between social habits and preferred habitats, (2) the relationship between species and prey preferences, and (3) the effect of predator avoidance on their social organization in order to assess the socio-ecological factors influencing otters. Females remain the core of their social stability. We show the major influence of habitats and feeding strategies (i.e. socio-ecology) of otters. The different species of solitary otters most often inhabit linear environments, such as freshwater ecosystems or wave-exposed marine coasts, and their habitat is often subject to disturbances that fragment their functional continuity. Social otters are more often found in extensive habitats with high plant cover, regular food resources and in areas with large predators compared to solitary species. The maintenance of regular resources and the fact that the main trophic resources are replenished rapidly might be determining factors driving sociality. Group-living and bachelor congregations among otters can also respond to pressure from large predators. This suggests that foraging, habitat use and the presence of large predators may be the drivers of sociality in otters. We conclude that most otters have a greater social potential than previously assumed, which is confirmed by their various vocalizations recently described.
Full-text available
Article
We studied habitat selection and home ranges of river otters (Lutra canadensis) living along the coastlines of Prince William Sound, Alaska, following the Exxon Valdez oil spill in late March 1989. Deposition of feces by otters at latrine sites that were heavily oiled was significantly less than for nonoiled sites in Herring Bay in June and July, but not during August 1989. Finer-scale measurements of habitat showed selection differed significantly on oiled (Herring Bay) and nonoiled (Esther Passage) study areas in 1990; otters selected steeper tidal slopes and sites with larger rocks on oiled than on nonoiled areas, based on characteristics of latrines and random sites. We believe otters avoided shallower slopes and protected areas with smaller rocks and gravel where oil persisted the longest. Thus, differences in habitat selection ostensibly were the result of a reduction in habitat availability caused by oil contamination. Otters on both study areas strongly selected old-growth forest; commercially logged areas in Esther Passage had no otter latrines. River otters on both areas also selected vegetated slopes (approaches to latrine sites) that were less steep. Home ranges of otters were about twice as large on the oiled area as on the nonoiled area, again suggesting that habitat for otters was reduced as a result of the oil spill. These outcomes were detected >1 year after the oil spill and suggest that there may be chronic effects of the oil spill on river otters.
Article
Mink (Mustela vison) frequently inhabited or traversed a residential, business, and industrial part of the Twin Cities, Minnesota, with little water or natural vegetation. At least one River Otter (Lutra canadensis) also resided on a small pond on a golf course in the area for several winter months.
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We describe of a nest-like structure at a natal den site in a shallow marsh in southern Indiana by an adult female River Otter (Lutra canadensis). Construction appeared to coincide with periods of high water, perhaps to avoid mortality of dependent pups from repeated flood events.
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The US Castor canadensis population has caused severe damage to valuable timberland through dam-building and flooding of bottomland forest. Since beaver populations are mobile, beaver extermination in controlled parcels results in beaver immigration from neighbouring less controlled parcels. This study develops a bioeconomic model that incorporates dispersive population dynamics of beavers into the design of a cost-minimizing trapping strategy. The optimality system for this problem is solved numerically. The validity of the theoretical model is examined using the bioeconomic data collected for the Wildlife Management Regions of the New York State Department of Environmental Conservation. The optimal trapping program causes the initially uneven population to eventually smooth out across the habitat. -from Authors
Article
We offer suggestions to avoid misuse of information-theoretic methods in wildlife laboratory and field studies. Our suggestions relate to basic science issues and the need to ask deeper questions (4 problems are noted), errors in the way that analytical methods are used (7 problems), and outright mistakes seen commonly in the published literature (5 problems). We assume that readers are familiar with the information-theoretic approaches and provide several examples of misuse. Any method can be misused-our purpose here is to suggest constructive ways to avoid misuse.