Results
The model that could best account for the effort of harvesting a Canada
lynx and the spatial temporal process in the southern periphery of
Ontario, Canada included the log transformed total number of furbearers
harvested and a thin plate smoother on the spatial coordinates (Table
S1). This model was 20.914 AIC units lower than all other models and its
AICw was 1.000. The spatiotemporal effort model had an
adjusted R2 of 0.586 and a deviance explained of
54.1%. Other than the total number of furbearers harvested, the 3 other
effort related predictors followed linear relationships (Figure S1). The
additive effect of the number of trapping units, the total area, and the
average price were not as important than the total number of animals
harvested. The probability of harvesting a lynx decreased with the total
area harvested while the 3 other predictors had a positive relationship.
Also, the influence of lynx pelt price was weak compared to the other
predictors.
The probability of harvesting a Canada lynx south of the boreal forest
across Ontario changed through time (Figure 3). During the late 1940s
and the early 1950s, the likelihood of harvesting a lynx was at its
lowest. However, in the mid-1960s the odds peaked across the southern
range and even trapping units found in the east had a high probability.
After this peak lynx period, it then became unlikely to harvest a lynx
in the east and this pattern continued to 2017. The odds of harvesting a
lynx peaked in both the west and central zones in the early 1960s and
again in the mid-1970s, then declined until the 2000s and increasing
slowly until 2017 to an overall probability of harvest higher than in
previous years.
To get a better idea of the range dynamics, we calculated the occupied
area of the southern range of each zone for each year (Figure 4). In
1950 the total extent of the southern lynx range was at its lowest and
occupied a total are of 19,118.2 km2. The extent of
the range peaked between 1963-1964 and occupied a maximum area of
147,483.5 km2. This was an area 7.7x larger than
during the crash in the late 1940s. From 1970 onwards, the southern
range varied much less in size compared to previous years. It declined
between 1970 and the late 1980s, but gradually increased until 2017 to a
size comparable to the early 1970s. There were also a few notable
decreases in range in the periods 1965-1972, 1983-1992 and 1995-2002.
In general, all 3 zones (west, central, and, east) followed similar
patterns. However, from 1957 to 1964 the east zone increased from
5,462.4 to 30,042.9 km2, which was a 6-fold increase
and occupied most of the Lanark and Renfrew County just east of Ottawa
(Figure 3). This increase was not as dramatic in the west and central
zones, where there was only a 1.5- and 1.3-fold increase. Although,
these two northernmost ranges were already closer to their maximum
extent of 65,548.2 and 54,623.5 km2, consequently they
could not have increased as intensely during this period. A smaller
range contraction in this same Lanark and Renfrew County area also
occurred in 1971 to 1973.
From the late 1950s to 2017, the west and central zones varied by
24,580.6 [40,967.6-65,548.2] and 16,387.0 km2[38,236.5-54,623.5]. The west zone reached its maximum area more
recently in 2013 and 2017, whereas the central zone reached its maximum
area multiple time in the periods 1960-1967 and 1970-1976. The east zone
varied quite differently. It increased dramatically twice in the period
1959-1973 and never reached these levels again. After this point the
range varied between 0 and 8,193.5 km2.
We calculated the number of years each sampling unit was within the lynx
southern range. Sampling units in the south were less frequently part of
the Canada lynx range (Figure S2). In the east zone, sampling units were
only part of the range on average 8.7 years over the 70-year time
period. In contrast, the west and central zones were part of the range
48.2 and 58.1 years, respectively.
We predicted that undisturbed areas with deep snow, an absence of
competitors, and close proximity to the boreal forest were more likely
to be part of the southern range. We found that 2 of 5 of these
relationships met our initial expectations (Table 1). Sampling units
that were more frequently found within the Canada lynx range were closer
to the boreal forest and had deeper average annual snow. We also
predicted that years with large numbers of hare and lynx in the boreal
forest, low number of competitors, and deep snow increased the extent of
the southern Canada lynx range. We found that only 1 relationship met
our initial expectations (Table 1); when the number of Canada lynx in
the boreal forest increased, the area of southern range increased the
following year.