DOI: 10.5061/dryad.771t4
title: Data from: Complementary food resources of carnivory and frugivory affect local abundance of an omnivorous carnivore

description: 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.
description: Measures of local
 grizzly bear abundance and surrounding road density and food
 supplyData 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.Nielsen_et_al_Oikos_data_file.csv