2.2. An animal body size perspective

2.2.1. Animal body size variation across the pillars of local food security

In northern Quebec, local food systems involve the consumption of at least 100 plant and animal species [9] ranging in body size from 3 g blue mussels [1] to 1300 kg belugas [2]. The importance of species body size as a key component of biodiversity is well-quantified and widely discussed in the ecological sciences literature [3]. Here we use animal body size variation as one approach to explore how biological diversity intersects with the four pillars of local food security.

The following discussion reflects results summarized in our recent review of how animal body size defines the availability, accessibility, adequacy, and use of wildlife species in local food systems across northern North America [4]. Then, in the next section, we consider how wildlife use varies with body size in Nunavik and Eeyou Istchee.

Small-bodied animals are, generally, more available than large-bodied animals because the species diversity of small-bodied animals is much greater than the diversity of large-bodied animals. For example, there are many more species of small-bodied songbirds than large-bodied waterfowl, more species of small-bodied rodents than large-bodied ungulates, and more species of small-bodied minnows than large-bodied salmonids. Furthermore, populations of small-bodied species also tend to occur at higher densities (individuals/area) than larger-bodied species. Nevertheless, smaller-bodied species often are present at lower biomass densities (kg/area) than larger species, especially when large-bodied species socially aggregate. Smaller-bodied species tend to grow and reproduce more quickly on a per gram basis than larger species and thus, relative to larger organisms, tend to live fast and die young. Since smaller species are typically characterized by higher per-capita production, sustainable harvest rates (as a percentage of population size) will generally decline with body size. Furthermore, smaller species will tend to rebound from episodes of over-harvest faster than larger species. However, the population size of smaller local food species will also tend to fluctuate faster and more than the population size of larger species.

Larger-bodied food species tend to be more accessible than small-bodied species in that they offer more calories that require less time to harvest. While the amount of time needed to pursue and process game increases with body size, caloric densities tend to increase more rapidly than the time required, leading to greater mean caloric returns per unit time in larger animals. However, the variability of returns also increases with body size; attempts to harvest large animals can yield many or few or no calories. Furthermore, the trend of increasing returns with body size may reverse for extremely large species due to increased pursuit and transportation costs. Larger-bodied species are generally more challenging to harvest, process, and transport than small-bodied species, but these challenges can be mitigated through cooperative hunting and adequate equipment.

The use of large-bodied species – particularly large mammals – tends to be disproportionate to their availability, according to archeological data, food recall studies, and harvest surveys from across northern North America. The body sizes of vertebrate species most often used as traditional food are typically hundreds to several thousands fold heavier than the most common body sizes available in the region. Citations, analysis, and detailed discussion of the general trends described in this section are available in [4].

2.2.2 Use and availability of wildlife in northern Quebec in relation to body size

​Here we relate relative use of local food species in Northern Quebec to the body size of those species, to assess whether large bodied species are used disproportionate to their diversity, as was found to be generally the case across North America and across a diversity of data sources. While northern Quebec local food systems include plants, invertebrates, and vertebrates, and size variation can be important across all forms of life, we focus here on harvest and consumption of vertebrates and, in particular fish, birds, and mammals. These taxa include many of the key species contributing to traditional food systems in northern Quebec and also have the most well-quantified body size data. Similarly, we focus exclusively on among species (inter-specific) body size variation because i) species-level estimates of mean body size are more readily available than regional, population, or individual-level estimates and ii) comparing species of vastly different body size renders results less sensitive to within species variation. All data are presented at the species-level, unless data sources quantified harvest or food use across multi-species groupings (e.g., ducks, seals, etc.). Of course, within-species size variation is also important, including regional differences associated with latitude, habitat, and subspecies or ecotype designations. Differences among individuals present within the same population is also important, but this intra-specific variation is not considered in detail here. This within population size variation is particularly important for fish because they are indeterminate growers and therefore defined by considerable age and diet-related size variation.

We obtained estimates of the total body mass of species harvested by Cree from [5]. Because estimated body size of species harvested by Inuit in Nunavik was not included in [6] and because many key species harvested by Inuit in Nunavik are rarely harvested by Cree in Eeyou Istchee, we estimated body mass data for species harvested in Nunavik using [7] compilation of mean adult body mass estimates for 9 993 bird and 5 400 mammal species. Determining a mean species body mass is more challenging for fish than for birds and mammals, because fish are indeterminate growers and therefore defined by considerable age and resource-related size variation. For fish, we estimated mean body mass estimates of 30,246 species using FishBase [8]. All data were presented at the species-level, but harvest surveys and food frequency questionnaires frequently included multi-species groupings (e.g. ducks, seals, salmon, etc.). To estimate body size of these aggregated categories, we identified the major harvested species present in Nunavik that comprised these categories [9] and averaged their species-specific body masses. This averaging implicitly assumes equal harvest of all species within the aggregate, which is unlikely to be the case, but the error introduced by this assumption will be minimized to the extent that size variation within the aggregate is much less than size variation across the entire range of harvested species. For food consumption data from Eeyou Istchee [10] and Nunavik [11], assumed animal body masses were the same as those applied to Eeyou Istchee and Nunavik harvest survey results, re-estimated for some of the new species group aggregates included as categories in the food frequency questionnaire.

Comparison of harvest and food use importance of fish, birds, and mammal species in relation to their species body mass and overall body size diversity distributions indicates that in the local food systems of northern Quebec, large animals in general, and large mammals in particular, are used disproportionately to their availability (Figure 23).

Broadly speaking, our analysis suggests patterns of harvest and food use in northern Quebec are consistent with North America-wide results presented by [4], in that harvest and food use tends to increase with body size, for fish, for birds, and in particular for mammals. Given species diversity declines as body size increases, our results show that large-bodied species are harvested and used for food disproportionate to their availability in northern Quebec. In many ways, this is an expected and unsurprising result. However, because body size is, in turn, correlated with many ecological and life history traits, including diversity, density, productivity, sustainable yield, generation time, and conservation status, this obvious pattern relates directly to the sustainability, resilience, and adaptive capacity of local food systems in an era of environmental and social change.

Our datasets describing the use of traditional foods contain entries for 298 unique vertebrate species in northern North America. This extraordinary biodiversity is the biological foundation for flexibility in traditional food systems in this region, and this only represents vertebrates. The additions of plants, fungus, and invertebrates complete food systems’ foundation of biodiversity. There are many documented instances of the flexible use of local biodiversity to adapt to changing socio-ecological circumstances (reviewed [4]) in order to maintain local food security in times of change. Emphasizing the importance of biodiversity to the security of traditional food systems, and the potential food value of species coming in all shapes and sizes, is made all the more urgent by the speed of socio-ecological changes being experienced by many communities and, in some cases, dramatic population declines in highly valued and heavily-relied upon species. Broadly speaking, we found larger traditional food species represented digestible biomass that was more available and accessible and, particularly with mammals, more frequently used. Conversely smaller species, while less available and accessible on a per kg basis, were more consistently available as they were more diverse and recovered more rapidly from harvest. All while being no more or less consistently adequate than larger species. Put more succinctly, while larger traditional food species were often more rewarding to harvest, smaller species were often more resilient. Adaptation strategies aimed at maintaining local food security through an era of environmental change and biodiversity decline, might focus on how to successfully harvest smaller-bodied species in greater numbers.

Our focus here on body size and its implications should not be taken to suggest that size-independent determinants of local food security are unimportant. Species body size is only one of a vast number of biodiversity traits relevant to their socio-ecology and local food use is influenced by many other size-independent factors. Nonetheless, there is evidence that body size scaling relationships play an important role in many socio-ecological systems, and our synthesis demonstrates the breadth of characteristics correlated with species body size in local food systems. The analysis presented here and the synthesis provided by [4] emphasizes the very tangible connections between animal body size, biodiversity, the security of local food systems, and opportunities for adaptation in an era of environmental change and biodiversity declines.

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