Some Estimates of Moose Populations in British Columbia During ...

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SOME ESTIMATES OF MOOSE POPULATIONS IN BRITISH COLUMBIA
DURING THE PERIOD 1950 - 1970
Abstract:
R.P. Finegan
University College, Cork
&
British Columbia Fish & wildlife Branch
Harvests of moose in British Columbia have
been well documented since 1950 in series of game
harvest questionnaire analyses.
This information,
taken in conjunction with checking station data
affording information on the sex and age composition
of the harvests, provides the basis for the calculation
of mimimum moose populations during the period 1950 -
1970. The estimates so calculated are compared with
the estimate of 300,000 given in the Inventory and
Evaluation of British columbia Game Animals:
B.C. Natural Resources Conference, 1963.
Fifteenth
Moose of three subspecies, Alces alces gigas, A.a.shirasi
and A.a.andersoni, occur in British Columbia.
The first two
are restricted in their distribution and the British columbia
Moose, A.a.andersoni predominates.
The moose population of
British columbia can be divided into a number of local populations
more or less geographically separated, but for the purpose
of this paper will be considered as a single population.
The
data utilised for estimation of the population in different
years is drawn from two sources:
the Cache Creek Records,
which provide factual information concerning the age and sex
of moose brought by hunters to the cache Creek Checking station;

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and the Game Harvest Questionnaire Analysis, or Hunter sample,
which provides information obtained from hunters through the
use of mailed questionnaires.
The reliability of the information
so obtained has been critically examined on a number of occasions
(Sugden 1950, Larkin 1953, Taylor 1958, Mccaughran 1963,
Finegan 1966) and can be regarded as satisfactory.
A previous estimate of the moose population has been given
as 300,000 (Robinson 1963) and the opinion was expressed that
"A knowledge of the average annual harvest provides a valid
basis for computing total population".
considerable data has
been collected since then and it has become possible to calculate
moose populations a little more closely.
The figures provided
here are crude and generally represent minimum estimates, but
the data is capable of refinement and the types of calculation
used can be applied equally well to local populations within
the general population.
METHODS
Three methods have been used to calculate minimum population
sizes during the period 1950 to 1970:
1. In the period 1950 - 1957 hunters were asked to report
the numbers of moose they had seen during their hunt.
The ratio of Number Seen:Number Shot is, therefore,
known, and by making the assumption that all animals in
the population were seen once this can be applied to

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the harvest estimate to produce a population estimate.
The possibility of bias due to overlap in observation,
when there can be no overlap in the record of numbers
shot, is reduced by the relatively low sampling levels
employed during this period (1 hunter in 15 to 1 hunter
in 10), and by the large amount of territory available
for moose hunting, giving low hunter density.
2. Animals harvested in an age class of yearlings or over
must have been alive in the previous year.
For a given
year the sum of harvests of successivelY older animals
in the following years provides the minimum number alive
in that given year.
Sex and age ratios, provided by
Cache Creek Records, can then be applied to give an
estimate of total population.
3. In a similar manner the minimum recruitment of yearlings
to the male population in a given year can be obtained
from the sum of harvests of successively older age classes
in the following years.
This provides an estimate of
the one-year-old class of males in the spring of that
year, to which can be applied the age class distribution
for the male component of the population in the same year
to calculate the total number of males.
Recruitment of
yearling females is assumed to be equal to that of
yearling males, as hunting mortality is low and evenly

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divided between male and female in the calf component of
the harvest of the preceding year.
The age class distribution
for the female component of the population is then
applied to calculate total number of females.
The sum
of male and female totals then affords an estimate of the
spring population of moose in the given year.
By use of these methods it has been possible to produce minimum
population estimates for most of the years within the period
1950 - 1970. The estimates with some supporting data are given
in the tables.
RESULTS AND DISCUSSION
supporting data are given in Tables 1, 2 and 3.
Estimated
populations are given in Table 4.

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CONCLUSIONS
Harvests of approximately 20,000 moose are being extracted
from a hunted population of 100,000 moose comprising the
spring population, or 135,000 moose comprising the fall population.
The male component is evaluated at approximately 40,000 from
which 13,000 are harvested annually.
The extraction rate is,
therefore, approximately 33%.
The female component is evaluated
at 60,000 from which 7,000 are harvested annually for an extraction
rate of 12%.
The juvenile component of 35,000 calves would
provide just sufficient recruitment to sustain the harvest of
bulls, with hunting mortality almost equal to natality. The
male component may, therefore, be regarded as fully utilized
and harvested at maximum extraction rate, but the population
estimates given refer only to the hunted population.
There are
many areas of British Columbia which are relatively inaccessible
and hunters are generally reluctant to hunt far from a road
because of the difficulty of bringing out the carcass and the
trophy.
In addition logging for pulp is a factor in the
creation of moose habitat and there are signs that moose are
still extending their range in British Columbia.
The actual
population of moose would, therefore, considerably exceed the
estimated hunted population of 135,000, and might well agree
with, or exceed, the estimate of 300,000 made by Robinson
in 1963.

Table 1.
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This shows the composition of moose harvests
between 1950 and 1970.
The data is incomplete for the
non-resident component of the harvest and the figures
shown do not include the numbers of moose killed in
subsistence hunting (Indians, prospectors, trappers);
illegally (poaching); or accidentally (road kills,
drownings).
Cow moose seasons contributed a female
component to the harvest from 1952 onwards.
It can
be seen that the numbers of moose harvested increased
from 4,129 in 1950 to a peak of 25,717 in 1968.
Generally the moose harvest can be said to have
stabilised since 1961, with numbers around the 20,000
mark, of which approximately 60% were males.
The
population was, therefore, sufficiently large to
sustain such harvests, which represent known mortality,
otherwise a decline in yield due to overharvesting would
have occurred during the period under study.

Table l. Composition of Moose Harvests 1950 - 1970
RESIDENT
NON RESIDENT
TOTAL
YEAR MALE FEMALE JUVENILE TOTAL MALE FEMALE JUVENILE TOTAL HARVEST
1950 3330 3330 (799) 4129
1951 4880 4880 1389 6269
1952 5546 1338 6884 NA 6884
1953 4684 81* 4765 NA 4765
1954 4115 778 4893 1015 5908
1955 4910 1133 155 6198 NA 6198
1956 4726 1457 319 6502 1245 7747
1957 6012 3281 608 9901 882 167 23 (1072) 10973
1958 8273 2578 695 11546 874 149 20 (1043) 12589
1959 8402 3262 536 12220 998 136 22 (1156) 13376 OJ
--J
1960 8145 2280 868 11293 1153 129 22 (1304) 12597
1961 10291 4101 862 15254 1532 300 46 1878 17132
1962 9873 5408 1394 16675 NA NA NA 2047 18722
1963 9531 5585 1394 16510 1546 445 74 (2065) 18575
1964 10541 6241 1071 17851 1486 499 71 (2056) 19909
1965 8897 5113 1215 15225 1872 793 159 2823 18048
1966 11027 7173 1740 19940 2105 880 184 3169 23109
1967 10353 7028 2016 19397 2257 867 158 3283 22680
1968 12590 8282 1597 22469 2247 859 142 3248 25717
1969 8901 5116 1188 15205 2383 608 152 3143 18348
1970 9883 5276 1291 16450 2318 691 141 3150 19600
* Low season in Wells Gray Park only
( ) Cache Creek Records: less than true number
NA Not available

Table 2.
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This table provides a breakdown of the age class
distribution of the moose population, and is derived
from Cache Creek Records, which provide information on
the age class distribution of the harvest.
The assumption
is made that the majority of moose hunters are relatively
unselective in taking bulls and that vulnerability and
desirability of moose differ little between age classes
over the age of yearling; the proportions of each age
class in the harvest may thus be regarded as representative
of the proportions of each age class in the population.
There is a clear difference between the age structures
of the male and female components of the population,
and this is reflected in the mean ages, calculated
as unweighted means in which the 5+ class is counted
only as five.
If the only major difference in mortality
of male and female moose is that due to hunting then
the figures illustrate that hunting mortality is large
enough to have a marked effect on the structure of
male population.

Table 2. Age Class Distribution and Mean of Moose population* 1961 - 1970
MALE
FEMALE
Age Class (Years)%
Age Class (Years)%
UNWEIGHTED
UNWEIGHTED
YEAR 1 2 3 4 5+ MEAN AGE 1 2 3 4 5+ MEAN AGE
1961 36.6 20.5 18.3 14.6 9.9 2.40 15.3 19.4 17.6 21.8 25.9 3.23
1962 27.8 25.4 19.9 12.1 14.8 2.61 25.1 18.9 18.5 14.1 23.4 2.92
1963 26.8 24.6 19.8 12.5 16.3 2.67 15.9 16.5 21.8 18.2 27.6 3.25
1964 28.8 19.5 21.3 15.9 14.6 2.68 19.4 15.8 20.2 18.7 25.9 3.16
00
1965 25.6 18.1 23.1 17.7 15.5 2.79 18.7 18.8 22.8 15.6 24.1 3.08
1966 25.9 22.4 20.0 15.0 16.8 2.75 19.1 17.3 18.5 19.6 25.4 3.15
1967 24.3 23.1 21.4 15.1 16.2 2.76 20.4 19.4 18.6 16.7 24.9 3.06
1968 24.0 24.0 20.7 14.1 17.3 2.77 20.3 19.7 19.9 15.8 24.2 3.04
1969 29.8 21.3 18.6 14.8 15.5 2.65 19.2 17.6 20.3 16.9 26.0 3.13
1970 33.4 19.9 10.4 7.3 29.0 2.79 26.5 16.8 8.5 7.6 40.6 3.19
\D
*Spring Population

Table 3.
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This table has been constructed to show the
estimated numbers in each age class in the spring
populations during the period 1961 - 1970. The
figures can be used to calculate minimum recruitment
to particular years or the minimum numbers alive in
particular years.
Thus, minimum recruitment to the
male yearling class can be calculated from the table
to provide the following:
Year
Recruitment
1961 11,877
1962 11,090
1963 10,452
1964 10,787
1965 11,073
1966 12,221
Recruitment to the years 1967 to 1970 cannot be
calculated in this fashion because of the limitation
imposed by the inexact nature of the 5+ age class.

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Table 3.
Estimated Numbers in Each Age Glass of
Moose Harvests 1961-70
MALE
Age Class (Years)
YEAR l~ 2~ 3., 4~ 5+ TOTAL
1961 4327 2436 2163 1726 1171 11823
1962 3162 2889 2263 1376 1683 11873
1963 2969 2725 2193 1385 1805 11077
1964 3452 2345 2562 1912 1756 12027
1965 2757 1949 2487 1906 1669 10768
1966 3388 2942 2626 1970 2206 13132
1967 3052 2913 2699 1904 2042 12610
1968 3561 3546 3071 2092 2567 14837
1969 3363 2403 2099 1670 1749 11284
1970 4075 2428 1269 891 3538 12201
FEMALE
Age Class (Years)
TOTAL
YEAR 1., 2~ 3., 4., 5+ TOTAL JUVENILE HARVEST
1961 673 854 775 959 1140 4401 908 17132
1962 1478 1113 1089 830 1378 5888 1461 18722
1963 959 995 1315 1097 1664 6030 1468 18575
1964 1308 1065 1361 1260 1746 6740 1142 19909
1965 1105 1110 1347 921 1423 5906 1374 18048
1966 1538 1393 1490 1578 2054 8053 1924 23109
1967 1611 1532 1469 1318 1966 7896 2174 22680
1968 1856 1801 1819 1444 2221 9141 1739 25717
1969 1099 1008 1162 967 1488 5724 1340 18348
1970 1581 1002 507 454 2423 5967 1432 19600

Table 4.
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Table 4 shows estimated populations, covering two
periods within the years 1950 to 1970.
The first period,
using Method 1 for calculation, covers the years
1950 - 1957 and provides a mean value for the fall
population of 84,960. The lowest value is 53,607
in the year 1956, and the highest value is 143,101 for
the year 1952.
Normal productivity would be insufficient
to account for the leap from one year's population to
the next in some cases, and the amount of variability
is largely attributable to the inexactitude of the
method of calculation. However, as the estimates can
only refer to the hunted population an increase from
one year to the next may be partially explained by
the expansion of hunting into previously unhunted,
or very lightly hunted, areas -
a process which was
taking place at that time.
During the same period the
ratios of male:female:juvenile show a trend in which
the number of females relatively diminished, while the
cow:calf ratio increased:
from 1.0 : 2.6 : 1.1 to
1.0 : 2.2 : 0.9. This is in keeping with the effects
of the antler less seasons which were instituted during
this period.

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Table 4.
Estimated populations Between the Years
1950-1970.
(a) Fall POEulations
Method of
Year calculation Male Female Juvenile Total
1950 13927 39771 16293 69991
1951 22198 72175 30581 126176
1952 28359 81554 33188 143101
1953 19288 51247 20609 91144
1954 1 14137 34197 12824 61158
1955 15736 34623 13946 64305
1956 13093 28423 12091 53607
1957 17630 37908 15881 71420
MEAN
1950-57 18046 47487 19427 84960
1961 30754
1962 31492
1963 31932
1964 2 33353
1965 33565
1966 37377
MEAN*
1961-66 33000 72600 29700 135300
*Mean rounded, using d ' : J=l 2.2 : 0.9
(b) BEring: pOEulations
Method of
Year calculation Male Female Juvenile Total
1961 32450 77627 110077
1962 39892 44183 84075
1963 39000 65735 104735
1964 3 37455 55603 93058
1965 43254 59213 102467
1966 47185 63984 111169
MEAN
1961-66 39873 61057 100930

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The second period covers the years 1961 to 1966,
using Method 2 for calculation, and provides a mean of
135,000 for the fall population. The male:female:
juvenile ratio applied in the calculation was 1.0
2.2 : 0.9. This was derived from the 1955 - 1957
cache creek Records, the closest data available, and
possibly favours the female component too highly if
the trend noted above continued into the second
period.
The male component is minimal, based on the
numbers which must have been alive in each year in
order to subscribe to later harvests.
Also during the second period of 1961 -
1966 the
spring populations, calculated by Method 3, show a mean
for the period of 100,930 consisting of 39,870 males
and 61,057 females.
The population estimates by this
method of calculation range from 84,075 in the year
1962 to 111,169 in the year 1966. There is thus a
high degree of consistency in the data, collected
independently in each of the years 1961 to 1970, which
forms the basis of the estimates.
The estimates for
the female component show more variation than those
for the male component, which is not surprising as
they depend on fewer observations because of smaller
numbers of females in the harvest.

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LITERATURE CITED
Finegan, R.P. 1965, 1966, 1967, 1968, 1970. Game Harvest
Questionnaire Analysis. B.C. Fish & wildlife Branch.
1964 - 1970.
Finegan, R.P. 1966. Reliability of the Hunter Sample: Game
Harvest Questionnaire Analysis 1966: 160-165. B.C. Fish
& Wildlife Branch.
Larkin, P. 1955. Hunter Sample Analysis. B.C. Fish & Game
Branch.
McCaughran, D.A.
Game Branch.
1962 & 1963. Hunter Samples.
1950 - 1963.
B.C. Fish &
Mccaughran, D.A. 1963. Goat Questionnaire Analysis 1963.
B.C. Fish & Game Branch.
Mccaughran, D.A. 1964. Game Harvest Questionnaire Analysis.
B.C. Fish & Wildlife Branch. 1964 - 1970.
Robinson, D.J. 1962. Management of Moose by Population Ratios.
42nd Annual Conference of the Western Association of State
Fish & Game Commissioners: Seattle, Washington.
Robinson, D.J. 1963. Inventory and Evaluation of the wildlife
Resources of British columbia. 15th British columbia
Natural Resources Conference.
Sugden, L.G. 1950. Hunter sample 1950. B.C. Fish & Game
Branch.
Sugden, L.G. 1950. Hunter Samples. B.C. Fish & Game Branch.
1950 - 1963.
Taylor, E.W. 1958. The 1958 Hunter Sample Follow-Up Survey.
B.C. Fish & Game Branch.
Taylor, M.M. and E.W. 1951-1961. Hunter Samples. B.C. Fish
& Game Branch. 1950 - 1963.
various Authors. Cache Creek Records. B.C. Fish & Wildlife
Branch. 1946 - 1970.