FECUNDITY AND SUMMER CALF SURVIVAL OF MOOSE DURING 3
SUCCESSIVE YEARS OF WINTER TICK EPIZOOTICS

Henry Jones1, Peter J. Pekins1, Lee E. Kantar2, Matt O’Neil, and Daniel Ellingwood1

1Department of Natural Resources and the Environment: Wildlife Program, University of New
Hampshire, Durham, NH, 03824, USA; 2Maine Department of Inland Fisheries and Wildlife, Research
and Assessment Section: Bangor, Maine, 04401, USA

ABSTRACT: Moose (Alces alces) populations in northern New Hampshire and western Maine
experienced 3 successive years of high winter tick infestations (epizootics) in 2014–2016 that resulted
in late-winter calf mortality rates >70%. To assess productivity in these populations, we measured
fecundity rates of yearling and adult cow moose, and neonatal and summer calf survival. Parturition,
fecundity, and survival were measured via direct observation by stalking VHF and GPS radio-collared
cows (n = 177) in May-August, 2014–2016. Calving rates for yearlings and adults averaged 0 and
57%, respectively; there was no twinning documented. Summer calf survival to August was high over-
all (83%), with 85% of the mortality occurring in the first week of life. Calving and twinning rates
declined since last measured in New Hampshire in 2002–2005 and were below the North American
average; conversely, summer survival of calves was considered normal. Given that optimal habitat
has increased in the past 15 years in the study area that is dominated by commercial forestry, lower
productivity is presumably related to the additive impacts of successive winter tick epizootics on
year-round condition of cows.

ALCES VOL. 53: 85–98 (2017)

Key Words: Alces alces, calving, fecundity, Maine, neonate survival, New Hampshire, pregnancy,
winter ticks

Many moose (Alces alces) populations
along the southern edge of their North
American range are declining, including in
Minnesota, Manitoba, Nova Scotia, Vermont,
New York, and New Hampshire (Murray et al.
2006, Broders 2012). The cause of decline
varies regionally, but it is generally asso-
ciated with the warming climate which likely
has an indirect influence through increasing
incidence of parasites and disease (Samuel
2004, Murray et al. 2006, Lankester 2010).
In northern New England, winter ticks
(Dermacentor albipictus) are suspected to
influence the population through periodic
widespread mortality of calves during epi-
zootics (Musante et al. 2010) which have

been occurring at an increasing frequency
in the last 15 years (Bergeron et al. 2013).
An epizootic event (>50% calf mortality)
was documented in northern New Hampshire
in 2002 (Musante et al. 2010), and acknowl-
edged to occur in northern New Hampshire
and western Maine in 2008 and 2011 by
the New Hampshire Fish and Game Depart-
ment [NHFG] and the Maine Department
of Inland Fisheries and Wildlife [MIFW]
(Bergeron et al. 2013). In these same areas,
epizootics occurred in 3 consecutive years
from 2014–2016. Mortality of radio-marked
10–12 month-old calf moose was 60–80%
between March and May from blood loss to
winter tick parasitism; the average winter

85



tick infestation on dead calves was 46,800
ticks (range = 34,800–63,600) (Jones 2016,
L. Kantar, MIFW, pers. comm.).

The population implications of succes-
sive or frequent epizootics with high calf
mortality rates are cause for concern among
regional moose managers. However, the
status and trajectory of a moose population
is also dictated by the number of calves
recruited into the population, termed here
as productivity, which is dependent on fe-
cundity, the number of calves born per cow,
and neonate and calf survival. Pregnancy,
calving, and twinning rates are parameters
that contribute to the fecundity rate of a
population (Van Ballenberghe and Ballard
2007). Productivity is influenced by the
nutritional condition of cows and calves, and
as such, allows for comparison with other
populations and overall assessment of health
(Schwartz 2007). Where productivity is high,
a population is more resilient to mortality
factors (Franzmann 2000), hence, an
important consideration given the recent
decline in the northern New England
moose population.

Winter ticks are known to cause popula-
tion decline in moose through widespread
mortality of calves during an epizootic year,
and suspected long-term effects due to reduc-
tion of adult cow fitness and productivity
(Musante et al. 2010, Bergeron et al. 2013).
High winter tick infestations presumably ex-
acerbate the negative energy balance of adult
cows in late winter and early spring due to the
compounding effects of substantial protein
deficit from blood loss (Musante et al. 2007)
and the nutritional deficiency of late winter
browse (Schwartz and Renecker 2007). Opti-
mal condition is relative to season, as moose
experience a negative energy deficit during
winter resulting in weight loss even on the
best range (Schwartz and Renecker 2007).
Yet, because gestational and early lactational
costs are met prior to spring green-up, avail-
ability of tissue energy, or minimizing weight

loss, is paramount to production. Poorer cow
condition from the additive effect of blood
loss to winter ticks may result in reduced fer-
tility, low yearling productivity, increased
age of first reproduction, and low twinning
rates (Musante et al. 2010), all of which
have been documented in New Hampshire
(Bergeron et al. 2013).

Given the increasing frequency of re-
gional epizootics and concurrently declining
estimates of productivity (Bergeron et al.
2013), it is critical to measure yearling and
adult female fecundity and survival rates of
calves to accurately assess the status and
trajectory of the regional population. This
study was designed to investigate the prod-
uctivity of two moose populations: one in
northern New Hampshire and the second in
western Maine. Similar harvest strategies
and ecological conditions between these
areas provided the opportunity to compare
and combine data sets. The specific objec-
tives of this research were to measure: 1)
adult cow pregnancy rates and parturition
dates, 2) calving and twinning rates of year-
ling and adult cow moose, and 3) summer
calf survival.

STUDY AREA
The 2 study sites were in northern New

Hampshire and western Maine, separated by
approximately 120 km. The New Hampshire
site was located in the eastern portion of
Coos County centered on the town of Milan
(Fig. 1). This site encompassed ∼1,250 km2
in NHFG Wildlife Management Unit
(WMU) C2 and portions of WMUs A2, B,
and C1, and replicated the study area of a
comprehensive population dynamics study
that occurred from 2002–2005 (Musante et al.
2010). Moose density was estimated as
0.46–0.87 moose/km2. The number of moose
hunting permits issued in 2013–2015 aver-
aged 28 either-sex and 10 antlerless-only per-
mits. The western Maine site extended north
and west of the town of Greenville to the

86

NH & ME PRODUCTIVITY – JONES ET AL. ALCES VOL. 53, 2017



Quebec border, including parts of Somerset,
Franklin, and Piscataquis Counties (Fig. 1).
This site was ∼5,620 km2 and encompassed
MIFW Wildlife Management District 8.
Moose density was estimated as 0.97–1.35
moose/km2. The number of moose hunting
permits issued in 2013–2015 averaged 175
bull-only and 25 antlerless-only permits.
Potential predators of moose calves were
black bears (Ursus americanus) and coyotes
(Canis latrans); bear density was estimated
as 0.38–0.58 bear/km2 in New Hampshire
(A. Timmins, NHFG, pers. comm.) and
0.65 bear/km2 in Maine (R. Cross, MIFW,

pers. comm.). White-tailed deer (Odocoileus
virginianus) were sympatric with moose
throughout the region and at an estimated
density of 6.34 deer/km2 in New Hampshire
(D. Bergeron, NHFG, pers. comm.) and 0.60
deer/km2 in Maine (K. Ravanna, MIFW,
pers. comm.).

Both study sites were privately-owned,
managed for commercial timber, and consid-
ered high quality moose habitat (15–20% of
the landscape in 4–16 year-old regenerating
forest; Ball 2017). The area was mountainous
(max elevation 1220 m) and geographically
diverse with lowland valleys, rolling hills,

Fig. 1. Study areas located in northern New Hampshire and western Maine, 2014–2016.

ALCES VOL. 53, 2017 JONES ET AL. – NH & ME PRODUCTIVITY

87



smaller mountains, and numerous lakes,
ponds, and rivers scattered throughout. The
dominant cover type was northern hardwood
forest consisting of American beech (Fagus
grandifolia), sugar maple (Acer saccharum),
and paper birch (Betula papyrifera). Conifer
stands of mostly red spruce (Picea rubens)
and balsam fir (Abies balsamea) were com-
mon at high elevation, with white cedar
(Thuja occidentalis) and black spruce (Picea
mariana) common in wet lowland sites
(DeGraaf et al. 1992). Year-round access
was available on logging roads, off highway
recreational vehicle (OHRV) trails, and
snowmobile trails. Private landowners per-
mitted access during the calving period
(May and early June) which typically coin-
cided with road-closures due to mud.

Climate data were available from the
National Climatic Data Center weather stations
at York Pond, Berlin, New Hampshire (ID:
GHCND:USC00279966, Lat/Long: 44.5002,
�71.333) and Jackman, Maine (ID: GHCN:
USC00174086, Lat/Long: 45.626, �70.246).
Annual ambient temperature ranged from 32
to �32 °C in both areas. For New Hampshire
and Maine, respectively, annual precipitation
ranged from 114.0 to 121.6 cm and 91.0 to
106.0 cm, and maximum snow depth ranged
from 17.8 to 66.0 cm and 30.5 to 106.7 cm.
The mean annual snowfall of 215.6 cm and
maximum recorded snow depths in 2014–
2016 (61.0, 66.0, and 35.6 cm) in New Hamp‐
shire were generally similar to those in Maine
(240.5 cm and 106.7, 53.3, and 43.2 cm). The
average weekly snow depth measured at open
sites in December–April 2013–2016 ranged
from 2.5–26.4 cm in New Hampshire and
5.8–48.7 cm in Maine; average weekly snow
depth did not exceed 70 cm at either site.

METHODS
Capture and marking

Animal capture and handling protocols
were approved by the Institutional Animal
Care and Use Committee at the University

of New Hampshire (IACUC #130805).
Cow and calf (both sexes) moose were cap-
tured by helicopter net-gunning and helicop-
ter darting (Aero Tech Inc., Clovis, New
Mexico, USA in 2014 and 2015; Native
Range Capture Services, Elko, Nevada,
USA in 2016) with a 4–6 person crew: the
pilot, animal handlers, and a veterinarian.
Captures occurred in January and were
competed in ≤ 7 days at each study site. Con-
centrations of non-collared moose were iden-
tified from helicopter and fixed-wing flights
prior to captures. Moose captured via darting
were immobilized with 3 mg of Carfentanil
and reversed with 300 mg of Naltrexone.
Additional captures in Maine included 6
adult cows collared in water using small
boats and a noose in August 2014 (Crossley
1987), and 2 adult cows darted roadside
using 2.2 mL of ketamine and reversed with
0.8 mL of medetomidine in December
2014. Moose captured via net gunning were
quickly removed from the net and restrained
with leg hobbles and blindfolded; the hand-
ling process typically lasted < 15 min.

Age classes were categorized as calves
(<1 year old), yearlings (>1 year but <2
years old), and adults (>2 years old) at the
time of the fall breeding season. As it can
be difficult to differentiate between yearling
and adult cow moose without observing
tooth wear, all cows were considered adults;
the relative size of each was checked with
the capture crew in an attempt to identify
any obvious yearling. The yearling age class
consisted of radio-marked female calves that
survived their first winter.

A 30 mL blood sample was taken from
the jugular vein to be used for subsequent
blood tests including pregnancy. Each moose
was fitted with numbered ear tags color-
coded by year (Allflex USA, Dallas, Texas,
USA) and a very high frequency (VHF) or
global positioning system (GPS) radio-collar.
Moose in New Hampshire were fitted with
either a VHF (n = 76; M2610B, Advanced

88

NH & ME PRODUCTIVITY – JONES ET AL. ALCES VOL. 53, 2017



Telemetry Systems, Isanti, Minnesota, USA;
Mod-600, Telonics, Mesa, Arizona, USA)
or GPS radio-collar (n = 54, GPS Plus Vertex
Survey Collar, Vectronic Aerospace GmbH,
Berlin, Germany); all moose in Maine
were fitted with GPS radio-collars (n = 142,
GPS Plus Vertex Survey Collar, Vectronic
Aerospace GmbH, Berlin, Germany). VHF
radio-collars had a motion sensor switch to
indicate a 4-h period without movement; col-
lars were continuously monitored with a
R4500S datalogger (ATS, Isanti, MN) con-
nected to a large omnidirectional antenna
(Cushcraft CRX 150) mounted centrally in
the study area. The GPS radio-collars col-
lected 2 GPS fixes daily (0000 and 1200 hr
EST) and had a VHF beacon that was
active at 0700–1900 hr EST; after 5 h of
non-movement, a motion sensor switch trig-
gered a “mortality message” via e-mail and
the pulse rate of the VHF signal increased.
Adults received collars sized to a standard
fit; calves received retrofitted collars that
allowed future expansion (see Musante et al.
2010). This research was part of a larger
study that also assessed cause-specific mor-
tality of the radio-marked moose.

Fecundity
Pregnancy status of each adult female

was determined from the blood samples col-
lected at capture using the pregnancy specif-
ic protein-B test (BioPRYN, Moscow, Idaho,
USA). Calving and twinning rates were mea-
sured principally through direct observation
by stalking adult and yearling cows within
sighting distance (i.e., walk-ins; Mech
1983, Musante et al. 2010). Calving rates
included the annual calving rate or the pro-
portion of cows documented as having a calf
each year, and the successive calving rate or
the proportion of cows that birthed in con-
secutive years. In New Hampshire, walk-ins
were conducted 2–3x weekly from 1 May–
1 July, and weekly thereafter until 1 August.
In Maine, movement was monitored through

daily GPS locations and walk-ins were
initiated when daily locations became highly
localized, indicative of birthing behavior
(Testa et al. 2000a, McGraw et al. 2014). If
localization did not occur, cows were checked
once weekly from mid-May to 1 July.

The age of neonatal calves was esti-
mated from their wet or dry appearance, mo-
bility, and coordination (Larsen et al. 1989,
Musante et al. 2010). The time span between
the initial calf sighting and the last observa-
tion of a cow without its calf was also used
to estimate age and birth date. In the absence
of direct observation, calves could be identi-
fied from tracks, vocalizations, and behavior
(mobility and grunting) of cows leading
their young. Parturition date and age of the
calf at first observation was estimated in
New Hampshire because walk-ins occurred
multiple times weekly; however, parturition
date and calf age at first observation in
Maine were assigned to weekly periods be-
cause walk-ins occurred ∼1x weekly which
increased the probability of missing some
early calf mortality (< 7 days). Direct obser-
vation was considered the best method to
document births and early survival because
it was minimally invasive and reasonable ac-
cess was available at both locations. Further,
because local spring green-up typically
occurs ∼2 weeks after the median birth date
(18 May; Musante et al. 2010), observations
were ideal during the immediate post-birth
period when most calf mortality occurs.

Monitoring of unmarked calves
Calf survival was measured intensively

for 60 d post-birth (summer survival) from
direct observation or sign (e.g., tracks,
beds, fecal matter, vocalizations) observed
during walk-ins; we assumed that surviving
calves would be near their radio-marked
mother. Survival of calves-at-heel was checked
2x and 1x weekly in New Hampshire and
Maine, respectively. If a calf was not ob‐
served ≥3 consecutive times over 2 weeks,

ALCES VOL. 53, 2017 JONES ET AL. – NH & ME PRODUCTIVITY

89



it was considered a mortality on the day mid-
way between the last confirmed observation
and the first missing date; specific cause of
death was never identified. An unmarked
calf was considered a mortality if the cow
died during this time period.

Analysis
Fecundity and calf survival rates were

compared between years at each study
site using a Chi-square independence test
and between study sites using Fisher’s
exact test. Calf survival was plotted on a
Kaplan-Meier survival curve with 95% con-
fidence limits and a Chi-square goodness-
of-fit test was used to compare the timing
of unmarked calf losses. Analyses were per-
formed using program R (v 3.2.2, Vienna,
Austria).

RESULTS
Fecundity

A total of 76 adult cows were monitored
for at least one calving season: 46 in New
Hampshire and 30 in Maine. The annual
pregnancy rate in New Hampshire ranged
from 76 to 88%, averaging 78% (n = 45);

there was no difference by year (χ2 = 0.54,
P = 0.76, Table 1). The annual pregnancy
rate in Maine ranged from 75 to 90%, aver-
aging 88% (n = 24); there was no difference
by year (χ2 = 0.28, P = 0.60, Table 1). Preg-
nancy rate did not differ between the study
areas (P = 0.32), and the combined average
was 81% (n = 69). Parturition occurred from
10–31 May (n = 83) in both study areas and
the median parturition date was 19 May
(n = 45, New Hampshire only). Birthing was
highly synchronous all years with 90% occur-
ring from 14–25 May. The mean age at first
observation (n = 29) was 1.8 d (SD = 1.4) and
only 2 calves were first detected at ≥5 days
old in New Hampshire; calf age at first observa-
tion was less specific in Maine due to differing
methodology (∼90% of calves were observed
during their first week of life).

Calving rates were similar in New Hamp-
shire (56%, n = 86) and Maine (58%, n = 62)
(P = 0.87), and among years in both states
(New Hampshire: χ2 = 2.60, P = 0.27; Maine:
χ2 = 0.43, P = 0.80) (Table 1). No births by
yearling cows (n = 17) or twinning by adults
(n = 148) was documented in either state;

Table 1. Annual and total observed fecundity rates of radio-collared adult cow moose in northern New
Hampshire and western Maine, during 2014–2016. Sample sizes are given in parentheses. Rates did not
differ by year or study area (P > 0.05).

Adult Cow Productivity %

Pregnancy Rate Calving Rate Successive Calving Rate

New Hampshire

2014 76 (21) 67 (21) NA

2015 75 (16) 45 (33) 29 (17)

2016 88 (8) 59 (32) 18 (28)

All Years 78 (45) 56 (86) 22 (45)

Maine

2014 90 (20) 55 (20) NA

2015 75 (4) 55 (20) 55 (11)

2016 NA 64 (22) 25 (12)

All Years 88 (24) 58 (62) 39 (33)

Combined 81 (69) 57 (148) 24 (78)

90

NH & ME PRODUCTIVITY – JONES ET AL. ALCES VOL. 53, 2017



thus, the fecundity rate was equivalent to the
calving rate. The successive calving rate
was 22% (n = 45, range = 18–29%) in New
Hampshire and 39% (n = 33, range =
25–55%) in Maine; the successive calving
rate did not differ between years (New Hamp-
shire: χ2 = 0.29, P = 0.59; Maine: χ2 = 1.04, P
= 0.31) or study area (P = 0.60), and overall
was 24% (n = 78) (Table 1).

Unmarked calf survival
Calf survival to 60 days averaged 77%

(n = 47) in New Hampshire and 94% (n =
36) in Maine (Fig. 2). There was no differ-
ence in annual survival at either site, ranging
from 64–87% in New Hampshire (χ2 = 2.04,
P = 0.36) and 91–100% in Maine (χ2 = 1.35,
P = 0.51). Although survival was not differ-
ent (P = 0.06) between study sites and the
combined rate was 86%, survival in Maine
was 17% higher. Nearly all mortality in
New Hampshire (82%) and Maine (100%)
occurred within 7 d post-birth when it was
higher than in the remainder of the 60-d per-
iod (NH: χ2 = 9.0, P = 0.01; ME: analysis
precluded).

DISCUSSION
Calf survival, pregnancy, and successive

calving rates were higher in Maine and could
be considered biologically different resulting
in a population trajectory ∼5% higher than
that in New Hampshire. However, we do
not believe that the populations are measur-
ably different because 1) the method for
detecting calves in Maine probably resulted
in Maine calves being a few days older
(with higher summer survival) at first detec-
tion than in New Hampshire, 2) the predom-
inance of pregnancy data originated from
only a single year in Maine, and 3) substan-
tial variation in the 2 years of successive
calving data reduces the potential accuracy
of these parameters to indicate any difference
between the study sites. Importantly, the New
Hampshire and Maine study sites demon-
strated similar trends of low adult fecundity
and high summer calf survival, suggesting
that a combined dataset is representative of
the larger study area, and that the moderate
variation in specific parameters was due to
inherent variance associated with method-
ology and sample size.

Fig. 2. Kaplan-Meier survival curve for unmarked calf moose from birth to 60 days old collected at
study sites in northern New Hampshire and western Maine, 2014–2016.

ALCES VOL. 53, 2017 JONES ET AL. – NH & ME PRODUCTIVITY

91



Most calf mortality in New Hampshire
(82%) and all in Maine occurred in the first
few days of life (≤7 days post-partum)
when calves are most susceptible to preda-
tion by black bears (Franzmann and
Schwartz 1985). Black bear density within
the study areas was high enough to incur pre-
dation (Ballard 1992), but calf survival was
much higher than in populations held at
low density by predation (76% loss in weeks
0–8; Gasaway et al. 1992). Calf survival in
Maine (94%) was higher than in populations
in Scandinavia with minimal predation
(87%; Ericsson et al. 2001), further suggest-
ing that early calf survival estimates in
Maine were probably artificially high. Calf
survival in New Hampshire was similar to
that measured previously (71%; Musante et al.
2010) and the combined New Hampshire and
Maine calf survival rate (88%) was similar to
that in Scandinavia (Ericsson et al. 2001).
Again, this survival estimate is probably
biased high due to the later detection date
of certain Maine calves; albeit, if so, the
Maine calving rate was underestimated.

The median parturition date (19 May)
and predominant calving season (14–25
May) were similar to those identified previ-
ously in New Hampshire (Musante et al.
2010) and central Ontario (Addison and
McLaughlin 1993), but earlier than in Alaska
(Testa et al. 2000b, Bertram and Vivion
2002). The timing and synchronous birthing
pulse (90% in 10 d) occurs across North
America (Keech et al. 2000, Testa et al.
2000b) and has been hypothesized as a re-
sponse to maximize use of high quality for-
age in summer (Bowyer et al. 1998) and to
minimize the influence of predation (Testa
et al. 2000b). Forage availability is probably
not as important in the northeastern United
States given the longer growing season rela-
tive to Alaska.

Our productivity measures were simi‐
lar to those associated with a declining popu-
lation, but these parameters often vary

regionally because they reflect unique and
multiple conditions in moose populations
(Table 2). The average pregnancy rate was
similar to the North American average
(84%; Boer 1992), but the yearling preg-
nancy and adult twinning rates were low
compared to other declining populations
(Boer 1992, Murray et al. 2006, Lenarz et al.
2010). Yearling pregnancy and adult twin-
ning rate are directly related and considered
indicators of the relative nutritional status
in moose populations (Franzmann and
Schwartz 1985, Boer 1992), and reflect habi-
tat quality and body weight (Adams and
Pekins 1995). The decline in yearling preg-
nancy from 20% in 2002–2005 (Musante
et al. 2010) to 0% in 2014–2016 corresponds
with declines in ovulation rate (proximate
measure for yearling pregnancy) and dressed
body weight measured from 1998 to 2009 in
New Hampshire (Adams and Pekins 1995,
Bergeron et al. 2013). The lack of twinning
in 2014–2016 also corresponds with a
decline in the corpora lutea count since
2002–2005 in New Hampshire, suggesting
a similar, but more subtle decline in phy‐
sical condition of adult cows (Bergeron et al.
2013).

It is hypothesized that the lack of repro-
duction by yearling cows is caused by
high annual infestations of winter ticks on
calf moose, and consequently, reduced fit‐
ness and fecundity of surviving yearlings
(Musante et al. 2010, Bergeron et al. 2013).
Calf moose that survive an epizootic event
(>50% mortality) are likely in poor condition
(McLaughlin and Addison 1986) which will
be reflected in lower body weight, ovulation
rate, and productivity as yearlings (Peterson
1977, Saether and Heim 1993, Keech et al.
1999). Adult cows with high winter tick
infestations are also presumed to be in poorer
condition due to the compounding ener‐
getic costs associated with winter ticks, ges‐
tation, and lactation while consuming a pro-
tein-deficient diet until spring green-up

92

NH & ME PRODUCTIVITY – JONES ET AL. ALCES VOL. 53, 2017



occurs 2–3 weeks post-birth (Musante et al.
2007, Schwartz and Renecker 2007). Reduced
productivity in adult cows is consistent with
the low rates of calving and successive calving
measured in 2014–2016.

Decline in physical condition during late
winter and early spring that stems from para-
sites is analogous to decline in physical con-
dition that influences productivity following
years of deep snow (Mech et al. 1987) or
harsh winter conditions (colder tempera-
tures, greater maximum depth and duration
of snow pack and shorter growing season;
Sand 1996). Reduced productivity from
a decline in physical condition of adult
cows is expressed by low twinning rates
(Mech et al. 1987, Sand 1996), lower calf:
cow ratios in autumn (Rolley and Keith
1980), and reduced weight and viability of
9-month old moose calves (Peterson et al.
1982). Because prenatal mortality is low in

deer and moose (Verme and Ulrey 1984),
these parameters likely reflect still births or
undersized and behaviorally abnormal calves
predisposed to mortality (Keech et al. 2000).

The potential effect of winter on product-
ivity during the subsequent year is attributed
to the inability of cows to fully recover or
compensate in one year (Mech et al. 1987).
The energetic costs of prior gestation and lac-
tation are evident in maternal adult cows that
have less fat, lower pregnancy rates, and
smaller embryos in autumn, and body condi-
tion in autumn is positively correlated with
pregnancy and calving rate, and negatively
with reproductive losses and neonatal mor-
tality the following spring (Testa and Adams
1998). These relationships illustrate that
adult cows must compensate for the demands
of pregnancy and lactation, and may require
a year to recover which reduces productivity
in the population (Mech et al. 1987). Poor

Table 2. Productivity measures from moose populations across the southern range of moose in North
America. Pregnancy rates were from serum progesterone levels, calving rates and twining rates from
direct observation, except for North American averages where pregnancy rates were from intrauterine
counts, and twinning rates from direct observation and intrauterine counts. Twinning rates are for yearling
and adult cows.

Location
Population
Change

Adult
Pregnancy

Rate
Yearling
Pregnancy

Calving
Rate

Twinning
Rate Source

New Hampshire
and Maine

Decreasing 82 0 57 0 This study

Northwestern
Minnesota

Decreasing 48 <20 45 19 Murray et al. 2006

North America Average
Decreasing

84 18 – 5 Boer 1992

Northeastern
Minnesota

Decreasing – – 78 – Lenarz et al. 2010

Norway n/a – – 77 – Stubsjøen et al. 2000
New Hampshire
2002-2005

Stable 85 20 75 11 Musante et al. 2010

Upper Peninsula
Michigan

Stable/
Increasing

74 – 65 19 Dodge et al. 2004

Southern Ontario Increasing 87 2 – 17 Murray et al. 2012
North America Average 84 49 – 33 Boer 1992

ALCES VOL. 53, 2017 JONES ET AL. – NH & ME PRODUCTIVITY

93



body condition in late winter-early spring
may affect productivity 3 years later because
calves born to cows in poor condition are
smaller and remain so (Peterson 1977, Keech
et al. 2000), reducing their survival and in-
creasing age to sexual maturity (Mech et al.
1987, Saether and Heim 1993, Keech
et al. 1999).

The large difference between our mea-
sured pregnancy rate (82%) and calving
rate (57%) can be attributed to a variety of
outcomes including resorption, still birth, or
undersized and behaviorally abnormal calves
predisposed to mortality; however, the spe-
cific outcome for any individual could not
be determined. Adult cows in poor condition
produce smaller neonates that experience
higher mortality and slower development
(Peterson 1977, Keech et al. 2000). Certainly
a portion of neonatal mortality could be
attributed to the compromised condition of
calves as a consequence of marginalized
adult cows, given the clear association of fre-
quent, high winter tick infestations and the
declining condition and productivity in this
population. Similarly, the low successive
calving rate (24%) suggests that maternal
costs and inadequate compensatory growth
prevented subsequent reproduction. The suc-
cessive calving rate was 3x higher (75%) a
decade earlier when a single epizootic oc-
curred in a 4-year period in New Hampshire
(Musante et al. 2010).

The effect of high winter tick infestations
on body condition and productivity is analo-
gous to malnutrition associated with poor
habitat (Albon et al. 1983, Albright and Keith
1987). But an important distinction is that
such malnutrition affects physical nutrition
in all age classes (Peterson 1977, Skogland
1983, Messier and Crête 1984), induces
starvation before old age (Bergerud et al.
1983), and high browsing rates are evident
(Albright and Keith 1987). Field-dressed
body weight, antler dimensions, and the onset
of sexual maturity are correlated with the

physical condition of moose (Schwartz and
Hundertmark 1993, Schmidt et al. 2007). Since
1988 these measurements have declined meas-
urably in yearling moose throughout the region,
yet only slight downward trends have occur‐
red in adult age classes (Bergeron et al. 2013,
Andreozzi et al. 2015). Yearling condition
reflects, in part, condition as a calf. The
marked decline in body weight and product-
ivity of yearling cows, yet subtle decline
in other age classes, reflects the negative
effects of frequent epizootics on productivity
(Bergeron et al. 2013). Neither this or the pre-
vious study (Musante et al. 2010) in the same
area attributed any mortality to starvation
(>350 radio-collared animals), and browsing
intensity on the landscape is considered
low-moderate overall (Bergeron et al. 2011).
Further, the rate of annual forest harvest in
the region has been relatively stable at
1–3% of the landscape since 1990, providing
continuous availability of optimal foraging
habitat (15–20% of the landscape in 4–16
year-old regenerating forest) through both
growth and decline of the moose population
(Ball 2017).

Moose are at the southern edge of their
continental range in this region and snow
depth of 70 cm that impedes moose mobility
and >90 cm that confines movement and
increases mortality (Coady 1974) occur in-
frequently. The winter of 2016 had nearly
snowless conditions and temperatures slight-
ly above normal (0.3°C, NCDC weather
data), yet an epizootic occurred and the trend
of low productivity continued. Given the
low adult productivity measured here, and
the lack of productivity and deterred growth
of yearlings, yet the lack of starvation and
the constant production of optimal foraging
habitat, it is evident that the winter tick,
not habitat, is the predominant influence
on this regional moose population. Con‐
tinued slow decline in this population is
predicted if the frequency of epizootics
remains high.

94

NH & ME PRODUCTIVITY – JONES ET AL. ALCES VOL. 53, 2017



ACKNOWLEDGEMENTS
Funding for this research was provided

through NHFG and MIFW in cooperation
with the United States Fish and Wildlife
Service - Wildlife and Sport Fish Restoration
Program, the University of New Hampshire,
and Safari Club International Foundation.
LightHawk LLC and the Maine Forest Ser-
vice were key partners for completing aerial
censuses. This research would not have been
possible without access to property owned
by American Forest Management, the
Conservation Fund, E. J. Carrier Inc., GMO
Renewable Resources, Hilton Timberlands
LLC, Maine Bureau of Parks and Lands,
Plum Creek, Moosehead Wildlands Inc., T.
R. Dillon Inc., and Wagner Forest Manage-
ment Ltd. The efforts of M. O’Neal and S.
McLellan in Maine, and numerous student
technicians in both states were critical for
the collection of these data.

REFERENCES

ADAMS, K. P., and P. J. PEKINS. 1995. Growth
patterns of New England moose: year-
lings as indicators of population status.
Alces 31: 53–59.

ADDISON, E. M., and R. F. MCLAUGHLIN.
1993. Seasonal variation and effects of
winter ticks (Dermacentor albipictus)
on consumption of food by captive
moose (Alces alces) calves. Alces 29:
219–224.

ALBRIGHT, C. A., and L. B. KEITH. 1987.
Population dynamics of moose, Alces
alces, on the south-coast barrens of
Newfoundland. Canadian Field Naturalist
101: 373–387.

ALBON, S. D., B. MITCHELL, and B. W.
STAINES. 1983. Fertility and body weight
in female red deer : A density-dependent
relationship. Journal of Animal Ecology
52: 969–980.

ANDREOZZI, H. A., P. J. PEKINS, and L. E.
KANTAR. 2015. Analysis of age, body
weight and antler spread of bull moose

harvested in Maine, 1980–2009. Alces
51: 45–55.

BALL, K. R. 2017. Moose and winter tick
epizootics in northern New England’s
changing climate. M.S. Thesis, Univer-
sity of New Hampshire, Durham, New
Hampshire, USA.

BALLARD, W. B. 1992. Bear predation on
moose: a review of recent American stud-
ies and their management implications.
Alces Supplement 1: 162–276.

BERGERON, D. H., P. J. PEKINS, H. F. JONES,
and W. B. LEAK. 2011. Moose browsing
and forest regeneration: a case study.
Alces 47: 39–51.

———, ———, and K. RINES. 2013. Tem-
poral assessment of physical characteris-
tics and reproductive status of moose in
New Hampshire. Alces 49: 39–48.

BERGERUD, A. T., W. WYETT, and B. SNIDER.
1983. The role of wolf predation in limit-
ing a moose population. The Journal of
Wildlife Management 47: 977–988.

BERTRAM, M. R., and M. T. VIVION. 2002.
Moose mortality in eastern interior
Alaska. The Jorunal of Wildlife Manage-
ment 66: 747–756.

BOER, A. H. 1992. Fecundity of North
American moose (Alces alces): a review.
Alces Supplement 1: 1–10.

BOWYER, R. T., V. VAN BALLENBERGHE, and
J. G. KIE. 1998. Timing and synchrony of
parturition in Alaskan moose: long-term
versus proximal effects of climate. Jour-
nal of Mammalogy 79: 1332–1344.

BRODERS, H. G., A. B. COOMBS, and J. R.
MCCARRON. 2012. Ectothermic res‐
ponses of moose (Alces alces) to thermo-
regulatory stress on mainland Nova
Scotia. Alces 48: 53–61.

COADY, J. W. 1974. Influence of snow on be-
havior of moose. Le Naturaliste Canadian
101: 417–436.

CROSSLEY, A. 1987. Summer pond use by
moose in northern Maine. M. S. Thesis,
University of Maine, Orono, Maine,
USA.

ALCES VOL. 53, 2017 JONES ET AL. – NH & ME PRODUCTIVITY

95



DEGRAAF, R. M., M. YAMASAKI, W. B.
LEAK, and J. W. LANIER. 1992. New
England wildlife: management of
forested habitats. General technical re-
port NE-144. Radnor, PA: United States
Department of Agriculture, U. S. Forest
Service, Northeast Forest Experiment
Station, Radnor, Pennsylvania, USA.

DODGE, W. B. JR., S. R. WINTERSTEIN, D. E.
BEYER, JR., and H. CAMPA III. 2004. Sur-
vival, reproduction and movements of
moose in the western Upper Peninsula
of Michigan. Alces 40: 71–85.

ERICSSON, G., K. WALLIN, J. P. BALL, and
M. BROBERG. 2001. Age-related repro-
ductive effort and senescence in free-
ranging moose, Alces alces. Ecology
82: 1613–1620.

FRANZMANN, A. W., and C. C. SCHWARTZ.
1985. Moose twinning rates : a possible
population condition assessment. Journal
of Wildlife Management 49: 394–396.

———. 2000. Moose. Pages 578–600 in S.
Desmarais and P. R. Krausman, editors.
Ecology and Management of Large
Mammals of North America. Prentice
Hall, Upper Saddle River, New
Jersey, USA.

GASAWAY, W. C., R. D. BOERTJE, D. V
GRANGAARD, D. G. KELLEYHOUSE,
R. O. STEPHENSON, and D. G. LARSEN.
1992. The role of predation in limiting
moose at low densities in Alaska and
Yukon and implications for conservation.
Wildlife Monographs 120.

JONES, H. F. 2016. Assessment of health,
mortality, and population dynamics of
moose in northern New Hampshire
during successive years of winter tick
epizootics. M. S. Thesis, University of
New Hampshire, Durham, New Hamp-
shire, USA.

KEECH, M. A., R. D. BOERTJE, R. T.
BOWYER, and B. W. DALE. 1999. Effects
of birth weight on growth of young
moose: do low-weight neonates compen-
sate? Alces 35: 51–57.

———, T. R. BOWYER, J. M. VER HOEF,
R. D. BOERTJE, B. W. DALE, and
T. R. STEPHENSON. 2000. Life-history
consequences of maternal condition in
Alaskan moose. The Journal of Wildlife
Management 64: 450–462.

LANKESTER, M. W. 2010. Understand‐
ing the impact of meningeal worm,
Parelaphostrongylus tenuis, on moose
populations. Alces 46: 53–70.

LARSEN, D. G., D. A. GAUTHIER, and R. L.
MARKEL. 1989. Causes and rates of
moose mortality in southwest Yukon.
Journal of Wildlife Management 53:
548–557.

LENARZ, M. S., J. FIEBERG, M. W. SCHRAGE,
and A. J. EDWARDS. 2010. Living on the
edge: viability of moose in northeastern
Minnesota. Journal of Wildlife Manage-
ment 74: 1013–1023.

MCGRAW, A. M., J. TERRY, and R. MOEN.
2014. Pre-parturition movement patterns
and birth-site characterisitics of moose
in northeast Minnesota. Alces 50:
93–103.

MCLAUGHLIN, R. F., and E. M. ADDISON.
1986. Tick (Dermacentor albipictus)-
induced winter hair-loss in captive moose
(Alces alces). Journal of Wildlife Dis-
eases 22: 502–510.

MECH, D. L. 1983. Handbook of Animal
Radio Tracking. University of Minnesota
Press, Minneapolis, Minnesota, USA.

———, R. E. MCROBERTS, R. O. PETERSON,
and R. E. PAGE. 1987. Relationship
of deer and moose populations to previ-
ous winter's snow. Journal of Animal
Ecology 56: 615–627.

MESSIER, F., and M. CRÊTE. 1984. Body
condition and population regulation by
food resources in moose. Oecologia 65:
44–50.

MURRAY, D. L., E. W. COX, W. B. BALLARD,
H.A. WHITLAW, M.S. LENARZ, T.W.
CUSTER, T. BARNETT, and T.K. FULLER.
2006. Pathogens, nutritional deficiency,
and climate influences on a declining

96

NH & ME PRODUCTIVITY – JONES ET AL. ALCES VOL. 53, 2017



moose population. Wildlife Monographs
166: 1–30.

———, K. F. HUSSEY, L. A. FINNEGAN, S. J.
LOWE, G. N. PRICE, J. BENSON, K. M.
LOVELESS, K. R. MIDDEL, K. MILLS, D.
POTTER, A. SILVER, M-J. FORTIN, B. R.
PATTERSON, and P. J. WILSON. 2012. As-
sessment of the status and viability of a
population of moose (Alces alces) at its
southern range limit in Ontario. Canadian
Journal of Zoology 90: 422–434.

MUSANTE, A. R., P. J. PEKINS, and D. L.
SCARPITTI. 2007. Metabolic impacts of
winter tick infestations on calf moose.
Alces 43: 101–110.

———, ———, ———. 2010. Characteris-
tics and dynamics of a regional moose
Alces alces population in the northeastern
United States. Wildlife Biology 16:
185–204.

NATIONAL CLIMATE DATA CENTER (NCDC).
2016. Climate Data Online Daily Sum-
maries January-December, 2014–2016.
<https://www.ncdc.noaa.gov/cdo-web/
datasets#GHCNDMS> (accessed Janu-
ary 2017).

PETERSON, R. O. 1977. Wolf Ecology and
Prey Relationships on Isle Royale. Na-
tional Park Service Scientific Monograph
Series No. 11. U. S. Government Printing
Office, Washington, D. C., USA.

———, J. M. SCHELDER, and P. W. STEPHEN.
1982. Selected skeletal morphology and
pathology of moose from the Kenai
Peninsula, Alaska and Isle Royale,
Michigan. Canadian Journal of Zoology
60: 2812–2817.

ROLLEY, R. E., and L. B. KEITH. 1980. Moose
population dynamics and winter habitat
use at Rochester, Alberta, 1965–1979.
Canadian Field-Naturalist 94: 1–9.

SAETHER, B-E., and M. HEIM. 1993. Eco-
logical correlates of individual variation
in age at maturity in female moose (Alces
alces): the effects of environmental vari-
ability. Journal of Animal Ecology 62:
482–489.

SAMUEL, W. M. 2004. White as a Ghost:
Winter Ticks and Moose. Natural History
Series, Volume 1. Federation of Alberta
Naturalists, Edmonton, Alberta, Canada.

SAND, H. 1996. Life history patterns in fe-
male moose (Alces alces): the relation-
ship between age, body size, fecundity
and environmental conditions. Oecologia
106: 212–220.

SCHMIDT, J. I., J. M. VER HOEF, and R. T.
BOWYER. 2007. Antler size of Alaskan
moose Alces alces gigas: Effects of popu-
lation density, hunter harvest and use of
guides. Wildlife Biology 13: 53–65.

SCHWARTZ, C. C.2007. Reproduction, Natality,
and Growth. Pages 141–145 in A. W.
Franzmann and C. C. Schwartz, editors.
Ecology and Management of the North
American Moose. Smithsonian Institu-
tion Press, Washington, D. C., USA.

———, and K. J. HUNDERTMARK. 1993.
Reproductive characteristics of Alaskan
moose. The Jorunal of Wildlife Manage-
ment 57: 454–468.

———, and L. A. RENECKER. 2007. Nutri-
tion and energetics. Pages 441–478 in
A. W. Franzmann and C. C. Schwartz,
editors. Ecology and Management of the
North American Moose. Smithsonian
Institution Press, Washington, D.C., USA.

SKOGLAND, T. 1983. The effects of den‐
sity dependent resource limitation on
size of wild reindeer. Oecologia 60:
156–168.

STUBSJØEN, T., B. E. SAETHER, E. J. SOLBERG,
M. HEIM, and C. M ROLANDSEN. 2000.
Moose (Alces alces) survival in three
populations in northern Norway. Canadian
Journal of Zoology 78: 1822–1830.

TESTA, J. W., and G. P. ADAMS. 1998. Body
condition and adjustments to reproduct-
ive effort in female moose (Alces alces).
Journal of Mammalogy 79: 1345–1354.

———, E. F. BECKER, and G. R. LEE. 2000a.
Movements of female moose in relation
to birth and death of calves. Alces 36:
155–162.

ALCES VOL. 53, 2017 JONES ET AL. – NH & ME PRODUCTIVITY

97

https://www.ncdc.noaa.gov/cdo-web/datasets#GHCNDMS�
https://www.ncdc.noaa.gov/cdo-web/datasets#GHCNDMS�


———, ———, ———. 2000b. Temporal
patterns in the survival of twin and single
moose (Alces alces) calves in southcen-
tral Alaska. Journal of Mammalogy 81:
162–168.

VAN BALLENBERGHE, V., and W. B. BALLARD.
2007. Population Dynamics. Pages
223–246 in A. W. Franzmann and
C. C. Schwartz, editors. Ecology and

Management of the North American
Moose. Smithsonian Institution Press,
Washington, D. C., USA.

VERME, L. J., and D. E. ULLREY. 1984. Physi-
ology and Nutrition. Pages 91–118 in
L. K. Halls, editor. White-tailed Deer
Ecology and Management. Stackpole,
Harrisburg, Pennsylvania, USA.

98

NH & ME PRODUCTIVITY – JONES ET AL. ALCES VOL. 53, 2017


	FECUNDITY AND SUMMER CALF SURVIVAL OF MOOSE DURING 3 SUCCESSIVE YEARS OF WINTER TICK EPIZOOTICS
	STUDY AREA
	METHODS
	Capture and marking
	Fecundity
	Monitoring of unmarked calves
	Analysis

	RESULTS 
	Fecundity
	Unmarked calf survival

	DISCUSSION
	ACKNOWLEDGEMENTS
	REFERENCES