Knowledge of behavioural compensation in response to nutritional demand and pasture conditions will be useful in designing supplementation program for farmed wapiti. q 2000 Elsevier Science
B.V. All rights reserved.
Keywords: Wapiti; Elk; Grazing; Activity pattern; CerÕus elaphus
1. Introduction
Northern ungulates synchronize annual reproduction with seasonal cycles in range forage characteristics so energy requirements are matched with forage quality and
quantity. However, within seasons, forage conditions vary, and herbivores respond proximally to these changes. Behavioural compensation is potentially the most important
Ž tactic for meeting additional energy demands of reproduction Gittleman and Thompson,
. 1988 .
Daily feeding activity involves several feeding bouts organized at different hierarchal Ž
. Ž .
levels feeding patch, feeding station and bite Gates and Hudson, 1983 . Daily foraging
may change with changes in pattern of feeding bouts and dynamic characteristics of Ž
. each bout. Jiang and Hudson 1993 concluded that wapiti forage in a manner consistent
Ž .
with Charnov’s 1976 Marginal Value Theorem. Ž
. Intake of grazed herbage can be described as the product of bite size BS , bite rate
Ž .
Ž .
BR , and grazing time Spedding et al., 1966 . BS has the greatest influence on Ž
. short-term intake, BR and grazing time are compensatory variables Forbes, 1989 , and
Ž .
all are sensitive to sward conditions Hodgson, 1985 . Although energy balance may ultimately control intake, it is proximally governed by a combination of plant structural
factors that influence ingestion rate, gut fill and the dynamics of gut repletionrdepletion, and social behaviour and environmental factors affecting the appetite–satiety complex
Ž
. Forbes, 1989 .
In this study, we explored the feeding behaviour of farmed wapiti hinds, specifically their response to seasonal variation in forage availability and nutritional requirements.
The objectives were to investigate how they alter their activity budgets and foraging Ž
dynamics on differing planes of nutrition, in order to meet the demands both time and .
energy of reproduction. The findings are expected to facilitate development of optimal supplementation programs for farmed wapiti.
2. Material and methods
The study was conducted at Ministik Wildlife Research Station, located 48-km southeast of Edmonton, AB on the Cooking Lake glacial moraine. Vegetation is
Ž .
classified as lower boreal mixedwood Strong, 1992 , consisting of an overstory of Ž
. Ž
. balsam poplar Populus balsamifera and trembling aspen P. tremuloides , and under-
Ž .
Ž .
storey dominated by beaked hazel Corylus cornuta and willow Salix spp. . Grass- Ž
. lands are primarily composed of Kentucky bluegrass
Poa pratensis , smooth brome
Ž .
Ž .
Ž .
Bromus inermis , white clover Trifolium repens , dandelion Taraxacum officinale , Ž
. and Canada thistle Cirsium arÕense .
Between June 1996 and November 1997, wapiti hinds were observed over seven periods, each lasting 16 days. Four stages of the annual reproductive cycle were
Ž .
Ž .
included: early gestationrautumn early November ; late gestationrspring early May ; Ž
. peak lactationrearly summer late Junerearly July ; and late lactationrlate summer
Ž .
late August . Two enclosures with similar plant species composition were established as Ž .
Ž . heavily H and lightly L grazed pastures, with areas of 2.6 and 2.2 ha, respectively.
Ž Commencing in early gestation 1996, smaller enclosures were employed H: 1.2 ha, L:
. 2.0 ha to enable more rapid defoliation in H. Prior to study commencement, H was
stocked with at least ten mature wapiti for 2 weeks to provide sufficient defoliation, while L had been free of grazing for at least 2 months. Between experimental periods, H
Ž .
was always stocked except during snowcover periods to ensure continuous defoliation, while L remained empty. Except during late gestation, pasture phytomass between
enclosures differed by at least 30. Ž
. Ž
Five bred wapiti hinds mean weight: 289 18 kg of similar age distribution mean .
age: 8 2.6 yr were randomly assigned to each pasture. All hinds raised calves which were present during lactation. Hinds were free-ranging and supplemented with concen-
Ž .
Ž .
trate alfalfa-barley pellets year-round and hay winter , except during study sessions, when all supplemental feed was withdrawn. To monitor condition, animals were
weighed on an electronic stock scale at the beginning and end of each of the seven 16-day trials. No attempt was made to hold animals without feed or water before
weighing.
Ž .
Foraging behaviour was observed during morning 0800–1130 h and afternoon Ž
. 1400–1700 h intensive grazing sessions on several days each study period. Cropping
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BRs bitesrmin were tabulated from 4–15-min sessions and corrected for nonforaging activities exceeding 30 s. BR observed during sessions less than 2 min duration were
discarded. Twice during each observational period, 10 = 20 cm plots paired with each grazing
observation were hand-plucked to ground level to emulate maximum possible removal by grazing wapiti. Samples were freeze-dried for 72 h at y60
8C to determine feeding Ž
2
. patch phytomass FPP, g DMrm . At the beginning, middle, and end of each 1997
session, five 0.25 = 0.25 m vegetation plots were sampled from randomly chosen grassland locations in each enclosure. These samples were oven-dried for 5 days at 60
8C Ž
. to determine pasture phytomass kg DMrha . Phytomass measurements were collected
Ž during a concurrent study at Ministik N. Donkor, unpublished data used with permis-
. sion .
Also paired with grazing observations, mean BS were estimated by hand-plucking 20 to 40 emulated ‘‘bites’’, to duplicate the amount and species composition of bites
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ingested by wapiti Hudson and Nietfeld, 1985 . Variations in wapiti incisor bar width and observer bias were corrected with the following equation:
Corrected Bite Size BS s BS = IrO 1
Ž .
Ž .
Ž .
where I is wapiti incisor bar width mm and O is width on observer hand that prehends Ž
. vegetation
mm . Although somewhat subjective, extensive observation of wapiti
grazing greatly improves representation of BS, and as well, past cervid studies on Ž
Ministik pastures have demonstrated reliable accuracy for this method Renecker and .
Hudson, 1985; Jiang and Hudson, 1992 . Activity budgets were determined using the predominant activity sampling method
Ž .
Hutt and Hutt, 1970 , whereby a behaviour was assigned if it occurred more than half of the given interval, irrespective of its distribution within the interval. This sampling
method is well-suited for captive free-ranging wapiti, as they are predictable and tend to sustain a behaviour for relatively long periods of time. For each group, behaviours were
Ž recorded at 10-min intervals over a 24-h period diurnal period only during peakrlate
. lactation 1996 , once per study period. Activities were categorized as foraging, bedded,
standing, and other, representing the only behaviours routinely demonstrated for at least 5 consecutive minutes. Other activities exceeding 5 min were rare, and included
Ž .
Ž .
movement running, walking , self-grooming, rubbing
against fence post or tree , Ž
. Ž
cow–calf interaction nursing, grooming , and cow–cow interaction agonistic, groom- .
ing . One-way analysis of variance was used to compare activity and foraging parameters,
Ž .
with reproductive season earlyrlate gestation, peakrlate lactation as fixed effects and Ž
random effects for individual hinds. Bonferroni’s pairwise multiple comparison SPSS, .
Ž .
1998 and Tukey’s HSD test SPSS, 1998 were used to analyze activity and foraging
Table 1 Seasonal foraging parameters and forage availability for wapiti hinds on heavily and lightly grazed pasture
Ž .
Ž 1997 only at Ministik Research Station, AB LG s late gestation; PL s peak lactation; LL s late lactation;
.
a,b,c
Ž . Ž
. EG searly gestation .
Row means that do not share superscripts differ p- 0.05
ANOVA Spring
Summer Autumn
SE Ž
. Ž
. Ž
. Ž
. LG
Early PL Late LL
EG HeaÕily grazed
a ab
b c
Ž .
Grazing time hrday 11.1
11.8 13.7
7.2 0.6
U
a ab
b b
Ž .
No. of bouts boutsrday 9.2
8.4 6.6
7.2 0.3
U UU
ab b
c a
Ž .
Duration minrbout 67.9
83.3 114.2
54.5 6.0
a a
b c
Ž .
BR bitesrmin 48.9
49.8 62.4
33.8 2.5
a a
a a
Ž .
BS mg 98
222 143
226 18
a a
a a
2
Ž .
Feeding patch phytomass g DMrm 183
321 314
257 26
U U
ab b
ab a
†
Ž .
Pasture phytomass kg DMrha 1625
2669 1680
1449 88
Lightly grazed
ab bc
b c
Ž .
Grazing time hrday 10.6
9.9 11.8
8.4 0.3
U a
a b
b
Ž .
No. of bouts boutsrday 10.4
12.0 7.4
7.4 0.5
U UU
ab b
a ab
Ž .
Duration minrbout 59.6
50.2 84.7
65.4 3.3
ab b
c a
Ž .
BR bitesrmin 44.6
45.5 61.4
40.6 1.9
a b
ab ab
Ž .
BS mg 155
339 210
281 23
a b
ab a
2
Ž .
Feeding patch phytomass g DMrm 263
580 498
312 42
U U
a b
b a
Ž .
Pasture phytomass kg DMrha † 1645
4875 3799
2152 243
U
Ž .
Ž .
Heavily grazed differs from lightly grazed pasture p- 0.01 within season t-test .
UU
Ž .
Ž .
Heavily grazed differs from lightly grazed pasture p- 0.05 within season t-test .
†
Ž .
From N. Donkor unpublished data used with permission .
parameters, respectively, to identify group means that differed significantly. Analyses of covariance were performed to detect whether age, sex, or day were covariates, and no
significant effects were revealed. If there was no significant difference between respec- Ž
. tive seasons among years, data were pooled. Student’s t-test SPSS, 1998 was used to
compare behaviour between pastures within seasons. Interrelationships among activity and foraging parameters were analyzed with non-linear regression. All statistical compu-
Ž .
tations were performed using SPSS Base 8.0 1998 , and p - 0.05 were accepted as significant. Means are reported with standard errors.
3. Results
