Data from: Complementary food resources of carnivory and frugivory affect local abundance of an omnivorous carnivore
Nielsen, Scott E., University of Alberta
Larsen, Terrence A., fRI; Hinton AB Canada
Stenhouse, Gordon B., University of Alberta
Coogan, Sean C. P., University of Sydney, University of Alberta
Published Sep 22, 2016 on Dryad.
Cite this dataset
Nielsen, Scott E.; Larsen, Terrence A.; Stenhouse, Gordon B.; Coogan, Sean C. P. (2016). Data from: Complementary food resources of carnivory and frugivory affect local abundance of an omnivorous carnivore [Dataset]. Dryad. https://doi.org/10.5061/dryad.771t4
A major unresolved question for omnivorous carnivores, like most species of bears, is to what degree are populations influenced by bottom–up (food supply) or top–down (human-caused mortality) processes. Most previous work on bear populations has focused on factors that limit survival (top–down) assuming little effect of food resource supply. When food resources are considered, most often they consider only the availability/supply of a single resource, particularly marine-subsidized or terrestrial sources of protein (carnivory) or alternately hard or soft mast (frugivory). Little has been done to compare the importance of each of these factors for omnivorous bears or test whether complementary resources better explain individual animal and population measures such as density, vital rates, and body size. We compared landscape patterns of digestible energy (kcal) for buffaloberry (a key source of carbohydrate) and ungulate matter (a key source of protein and lipid) to local measures in grizzly bear Ursus arctos abundance at DNA hair snag sites in west-central Alberta, Canada. We tested support for bottom–up hypotheses in either single (carnivory [meat] versus frugivory [fruit]) or complementary (additive or multiplicative) food resources, while accounting for a well-known top–down limiting factor affecting bear survival (road density). We found support for both top–down and bottom–up factors with complementary resources (co-limitation) supported over single resource supplies of either meat or fruit. Our study suggests that the availability of food resources that provide complementary nutrients is more important in predicting local bear abundance than single foods or nutrients (e.g. protein) or simply energy per se. This suggests a nutritionally multidimensional bottom–up limitation for a low density interior population of grizzly bears.
Measures of local grizzly bear abundance and surrounding road density and food supply
Data fields: 1) "DNA_sampling_cell_ID" is the 7x7 km cell used to allocate hair snag sites and used as a random effect in models; 2) "Session_number" is the 2 week session number of sampled site between 25 May and 17 July 2004; 3) "Number_grizzlybears" is the unique bears detected at hair snag site; 4) "Road_density_7440m" is the moving window road density (km/km^2) within a 7440 m radius window calculated in ArcGIS; 5) "Shep_can_fruit_DigE_1690m" is the modeled digestible energy (kcal) of Shepherdia canadensis fruit within a 1690 m radius of the hair snag site summarized in an ArcGIS moving window; 6) "Shep_can_fruit_DigE_7440m" is the modeled digestible energy (kcal) of Shepherdia canadensis fruit within a 7440 m radius of the hair snag site as summarized in an ArcGIS moving window; 7) "Ungulate_DigE_7440m" is the digestible energy (kcal) of ungulate matter within a 7440 m radius of the hair snag site as summarized in an ArcGIS moving window; 8) "NDVI_JulyMax_1690m" is the Natural Difference Vegetation Index (NDVI) maximum value in the month of July from MODIS remote sensing data during the year 2006 with values averaged within a 1690 m radius of the hair snag site as summarized in an ArcGIS moving window; 9) "NDVI_JulyMax_7440m" is the Natural Difference Vegetation Index (NDVI) maximum value in the month of July from MODIS remote sensing data during the year 2006 with values averaged within a 7440 m radius of the hair snag site as summarized in an ArcGIS moving window.