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Ontario Wildlife Food Survey, 2016
Abstract and Figures
Fruit production by trees and shrubs varies considerably among years, and consumers respond behaviorally and numerically to the associated fluctuations in food supply. For example, American black bears (Ursus americanus) are more likely to come into conflict with humans when berries and nuts are scarce, and small mammal abundance tracks fluctuations in seed production at a 1-year lag. Therefore, data describing variation in fruit production could facilitate a better understanding, and in some cases prediction, of wildlife behaviour and population dynamics. The Ontario Ministry of Natural Resources and Forestry (MNRF) has ranked fruit production by various trees and shrubs within districts across Ontario since 2004, and over a subset of the province since 1998. Here we present results of surveys conducted in 2016, and time series of fruit production rankings within eastern and western portions of Great Lakes–St. Lawrence (GLSL) and boreal forest regions. In 2016, soft mast production was average, providing low to moderate food for black bears and small mammals across GLSL forests. In the eastern boreal these values were low. Fall forage in the form of acorns was largely lacking over much of central Ontario whereas beechnut quantities were average in many areas. Over most of our time series, food availability for black bears and small mammals varied synchronously across a vast landscape including most of southern and northeastern administrative regions. Some tree species also periodically produced bumper crops simultaneously over large areas. Landscape-scale patterns were not as apparent in Northwest Region, where variation in fruit production was not synchronous across districts or species.
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We used scat analysis to investigate temporal variation in the food habits of American Black Bears (Ursus americanus) in the boreal forest of northern Ontario. specifically, we examined whether there was a seasonal shift in foraging over three years (1990-1992) and which foods, if any, varied in occurrence among years. American Black Bears ate foods ranging from green vegetation in the spring to ants in mid-summer and berries and nuts in late summer and fall. Late summer berry forage, especially blueberries (Vaccinium spp.), varied greatly among years. American Black Bears in northern Ontario consumed a variety of foods opportunistically. Understanding how American Black Bears in northern Ontario exploit food resources and how these food items vary among years can provide insights into demographic processes and help wildlife managers better anticipate changes in the structure of the harvest of American Black Bears and in human-bear conflict levels. in northern Ontario, forest management practices that increase the availability of early successional species would be beneficial to American Black Bear populations.
Breeding systems and pollination requirements of two wild lowbush blueberries, Vaccinium angustifolium and V. myrtilloides, in the Canadian boreal forest in the Chapleau Crown Game Preserve, Ontario, were tested. Fruit production, size and seediness were significantly higher in samples exposed to natural pollination than in those cross- or self-pollinated by hand. There were no significant differences among artificial treatments (variously hand-pollinated and bagged) except when cross-pollination (xenogamy) was done by insect pins. In V. angustifolium, the density of flowering varied with forest age (canopy closure). It was most in open areas and least in the sites with the most mature forest. Although fruit-set and seediness varied among forest habitats of different ages, there were no significant differences between sites in forests of different ages. Thus, pollination seems to be similarly effective no matter the age of the forest. In both species, fruit-set in 1992, which had severe June frosts, was markedly poorer than that in 1993 when the flowers suffered little frost damage. The combined number of complete and incomplete seeds from the fruit among the breeding and pollination systems tested were similar; however, the ratio of complete seeds to total seeds was greater from cross-pollinated than from self-pollinated flowers. Our observations indicate that there is little natural fruit-set without insect-mediated cross-pollination and that cross-pollination provides much better fruit and seed-set than does self-pollination.
Three sets of time series on plant seed production and herbivore number were analysed in order to test the proposed "mast depression hypothesis", which states that cyclic population fluctuations of herbivores is a result of cyclic seed cropping of plants, because high seed crops, termed masts, are produced at the expense of chemical defence against herbivores. From 1880 to 1916, the annual export of small game, mainly willow grouse Lagopus lagopus, from Oslo was positively correlated with the quantity of berries, mainly bilberry Vaccinium myrtillus and cowberry V. vitis-idaea, exported in the previous year. In Vegårshei, South Norway, the intervals between years of high access of bilberry and cowberry varied from 3 to 5 yr during 1952-95. All mast years were followed by a year of high microtine population. In South Norway, mast years of Norway spruce Picea abies, which usually shows high flowering intensity in the same years as mountain birch Betula pubescens, occurred with a mean interval of 9.8 yr (range 7-13 yr) during 1930-85. Almost all attacks of autumnal moth Epirrita autumnata on mountain birch were reported after a mast year of forest trees. The synchronised flowering cycles of plants indicate that high seed crops are induced by some climatic conditions. Allocating a large proportion of available resources, including chemical defence compounds, to seed production in some years of advantageous conditions may improve a plant's total life-time reproduction, despite the subsequent risk of serious damage by herbivores.
When Keith (1963) published his ‘Wildlife’s 10-year cycle’, available information on the theme was minimal. Many theories were no more than conjectures. In 1961, realizing that further theorizing would get him nowhere, Keith and a team of researchers from the Wisconsin school of wildlife ecology, launched a long-term field study on snowshoe hare (Lepus americanus) populations near Rochester, Alberta. A number of important papers from this study have appeared since then, including the monograph (Keith and Windberg, 1978) that provides a nearly complete 15-year set of demographic data. I shall call this work ‘the Rochester study’.
Ursus americanus were studied in the Great Smoky Mountains, Tennessee. Females were in estrus from 5 June to 12 September, with most breeding activity from 24 June to 21 July. Females in ground dens had mean litter sizes of 2.6 cubs; mean litter size for females with yearlings in ground dens was 2.2. Most females gave birth for the first time at 4 or 5 years of age (range 2-5 yr). Females usually gave birth every other year, but 8 of 23 females exhibited skips between years. Loss of entire litters was not common although there was mortality within litters. Availability of hard mast during fall affected minimum reproductive age, productivity and cub survival. Maximizing hard mast production and promoting secondary fall foods should enhance reproduction and survival. -from Authors
Conducted an 8-yr study of flower and acorn production in white oak Quercus alba, red oak Q. rubra and black oak Q. velutina in E-central Missouri. Red oak and white oak showed a greater degree of mast-fruiting than did black oak. Within a species, individuals tended to produce large acorn crops in the same years, but each species differed in which years they produced large crops. The size of a given acorn crop was determined by both flower abundance and survival of flowers to fruit. The first principal component explained the largest amount of the variation in black oak (R2 = 0.55) and red oak (R2 = 0.89). In white oak, two principal components combined to explain 77% of the variation in acorn production. Weather variables associated with these principal components included spring temperature (positive effect) and summer drought (negative effect). Past acorn production had a major impact on the size of the current acorn crop, with each species showing a different pattern. In black oak, the current acorn crop was negatively correlated with the crop 3 yr prior but positively correlated with the crop 2 yr prior. In red oak, acorn crop size 1, 2, and 3 yr prior had negative correlations with current acorn crop, while acorn crop size 4 yr prior was positively correlated. In white oak, there were negative correlations between acorn crop size and crop size 1, 2, and 4 yr prior but a positive correlation with the acorn crop size 3 yr prior. Data are consistent with the hypothesis that mast-fruiting species must store resources during some years in order to produce a mast crop. The patterns of acorn production for black, red, and white oak are apparently not simply responses to weather events but are also a function of prior reproductive events. This suggests that masting is an evolved reproductive strategy. -from Authors
The population cycles of microtine rodents in northern Finland have been continuously followed since the late 1940's. Plant reproduction (flowering, berry and seed production, and the subsequent formation of young rhizomes etc.) has been monitored since 1972. Cycles of sympatric microtines were synchronous and were characterized by synchronous changes in the condition of the rodents. These facts cannot be explained by intrinsic factors, competition or predation alone. Plants are also characterized by 'cyclicity' in reproduction and growth, which are synchronous among many plant species. The basic rhythm is not modified by rodents. The short growing season is considered to be a primary factor for cyclic reproduction in plants. Plants need to accumulate reserves for several summers before they can flower; this accumulation and exhaustion of resources is reflected in microtine nutrition and population dynamics. There seems to be a threshold level of temperature sums which activates flowering. Changes in food supply (plant rhythms, local overgrazing, defence) are the primary factors triggering the population decline. Other extrinsic factors such as predation and possibly diseases contribute to the depth of the decline. -from Authors
Data from 18 adult female Ursus americanus from an exploited population in W Massachusetts bearing 62 cubs in 27 litters (31 M, 31 F) provided insights into nutrition and population dynamics. 26 of 28 females with access to high fat and carbohydrate mast diets produced cubs, but 10 of 10 females with low carbohydrate fall diets failed to produce cubs. 41 cubs (21 M, 20 F) in 18 families were followed. Overall mortality of cubs was 41% by 1 yr and 61% by 2.5 yr (subadult). Mortality was much higher for male cubs, even before familiy breakup (62 vs 20% by age 1, 91 vs 35% by age 3). Most cub mortality (76%) occurred between 1.5-5 months of age. Human interactions, behaviour of the mother, and disease influenced cub survival. 13 of 20 female cubs survived to adulthood, and all but 1 stayed within their natal areas. 8 of 21 male cubs survived until dispersal, but 6 of 8 were shot by hunters while dispersing at age 2.5. Only 2 of 21 male cubs survived to adulthood. There was no evidence of competition for food or space. Fall mast availability appeared to influence bear densities through the number of female cubs born. -from Authors