Forage quality's influence on mule deer fawns

Tollefson, Troy N.; Shipley, Lisa A.; Myers, Woodrow L.; Dasgupta, Nairanjana

doi:10.1002/jwmg.113

Cited by 42 publications

(45 citation statements)

References 35 publications

(57 reference statements)

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“…Individuals born under favorable conditions can in turn reproduce earlier, reach a higher body mass and have a higher reproductive success compared to individuals born under less favorable conditions (Gaillard et al 2000, Bonenfant et al 2009). Consequently, calves of mothers receiving supplementary feeding should benefit from greater v www.esajournals.org maternal care via for example higher milk quantity and quality (richer fat content), as shown in mule deer (Tollefson et al 2011) and elk (Cook et al 2004), allowing them to maximize their growth (e.g., in red deer: Clutton-Brock et al 1982;elk: Smith et al 1997) and overwinter survival (e.g., in three species of mountain ungulates: Pettorelli et al 2007). …”

Section: Effects Of Supplementary Feedingmentioning

confidence: 99%

Combined effects of long‐term feeding, population density and vegetation green‐up on reindeer demography

et al. 2013

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Abstract. Large herbivores living in seasonal environments are generally food-limited through density dependence and climatic factors. This may result in starvation and increased mortality in winter and reduced fecundity the following summer. Variability in winter conditions has the potential to create persistent fitness differences at the cohort-and the individual-level in iteroparous species. Using a 9-year dataset from two herds of individually marked free-ranging reindeer we assessed whether population growth rates, somatic allocation (female body mass) and reproductive allocation (reproductive success and calf body mass) were affected by supplementary feeding, population density and the timing of the onset of spring (i.e., vegetation onset). The supplementary fed population had a higher population growth rate, the females were more likely to reproduce and their calves were heavier than in the control population. Female body mass was negatively related to timing of vegetation green-up in both herds. Since both populations increased in the last decade we found support to our prediction that density-dependence negatively affected our study herds. Indeed, density negatively affected growth rates, female body mass, reproductive success and calf body mass in both populations and, as expected, this effect was more marked in the control herd. We suggest that food supplemented females may, at least partially, be able to compensate for the energetic costs of negative density-dependence following late vegetation green-up while control females may not. Our findings reveal that late winter conditions have an important limiting role in the study area and that density-dependent food limitation in late winter/early summer acts as a main factor affecting our reindeer population.

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Section: Effects Of Supplementary Feedingmentioning

confidence: 99%

Combined effects of long‐term feeding, population density and vegetation green‐up on reindeer demography

et al. 2013

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“…Investigators have demonstrated associations between NDVI and plant primary productivity and biomass (Tucker and Sellers 1986, Reed et al 1994, Thoma et al 2002, but less is known about the utility of NDVI for predicting the nutritional quality of ungulate forages, a key factor driving patterns of ungulate behavior and demography (Fryxell 1991, Tollefson et al 2011. Investigators have demonstrated associations between NDVI and plant primary productivity and biomass (Tucker and Sellers 1986, Reed et al 1994, Thoma et al 2002, but less is known about the utility of NDVI for predicting the nutritional quality of ungulate forages, a key factor driving patterns of ungulate behavior and demography (Fryxell 1991, Tollefson et al 2011.…”

Section: Introductionmentioning

confidence: 99%

NDVI exhibits mixed success in predicting spatiotemporal variation in caribou summer forage quality and quantity

Johnson

Gustine²,

Golden

et al. 2018

Ecosphere

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The satellite-derived Normalized Difference Vegetation Index (NDVI) is commonly used by researchers and managers to represent ungulate forage conditions in landscapes across the globe, despite limited information about how it compares to empirical measurements of forage quality and quantity. The application of NDVI as a forage metric is particularly appealing for studying migratory caribou (Rangifer tarandus) in remote Arctic ecosystems, where field assessments are logistically and financially prohibitive, and climate-mediated changes in vegetation have been hypothesized to influence population declines. To determine the utility of NDVI for adequately representing caribou forage conditions, we compared NDVI derived from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery to empirical measures of caribou forage biomass, nitrogen, digestible nitrogen, and digestible energy within the summer range of the Central Arctic Caribou Herd on the North Slope of Alaska. Specifically, we determined the strength of forage-NDVI relationships at the start of the growing season and across the summer, assessed the efficacy of NDVI variables for modeling spatiotemporal variation in field measurements of different forage components, and used long-term MODIS data to estimate temporal changes in forage between 2000 and 2016. We found that NDVI values were weakly correlated with caribou forage quality at the start of the growing season and throughout the summer. Although linear models of forage-NDVI relationships performed poorly, NDVI variables (NDVI and the number of days from when NDVI reached its maximum value) were useful for modeling spatiotemporal variation in empirical measurements of forage components across the growing season, but only when we incorporated nonlinear forage-NDVI relationships and other habitat covariates. Phenological advances in the date of peak NDVI were associated with significant changes in forage conditions, particularly nitrogen, which exhibited earlier seasonal declines. Using long-term MODIS data, predicted values of forage nitrogen declined between 2000 and 2016, driven by exceedingly low values in 2014 and 2015. Given our results, we caution the application of NDVI as a general (linear) proxy of caribou forage conditions across the growing season, and encourage practitioners to use NDVI variables to model spatiotemporal variation in specific forage conditions from empirical field data, accounting for nonlinear forage-NDVI relationships.

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“…In seasonal and unpredictable environments, where food availability can fluctuate, females should ensure that they retain sufficient body reserves to survive food‐limited periods by reducing reproductive output accordingly (Therrien et al , Bårdsen et al ). When maternal nutrition is compromised, young are smaller at birth (Keech et al , Monteith et al ), nursing and maternal care decline (Rachlow and Bowyer , Therrien et al , Scornavacca et al ), growth of young is suppressed (Festa‐Bianchet and Jorgenson , Martin and Festa‐Bianchet , Tollefson et al ), and mortality of young increases (Therrien et al , Monteith et al , Scornavacca et al ). This conservative life‐history strategy transfers the costs of reproduction from females to their young (Festa‐Bianchet and Jorgenson , Martin and Festa‐Bianchet , Monteith et al ).…”

Section: The Trifecta: Age Genetics and Nutritionmentioning

confidence: 99%

Horn size and nutrition in mountain sheep: Can ewe handle the truth?

et al. 2017

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Horns, antlers, and other horn-like structures are products of sexual selection, confer reproductive advantages, and are heritable and honest indicators of individual quality. In addition to serving key biological functions, horns and antlers garner societal interest that, when combined with the powerful motivation to acquire trophy animals, likely has spawned a growing hornographic culture fixated on males with exceptional horn-like structures. The concern that harvest of large, fast-growing males may cause evolutionary change to the very trait being sought has been the source of controversy in the popular and scientific literature over the past 2 decades. Mountain sheep (i.e., bighorn and thinhorn; Ovis spp.), possibly the only large ungulates in North America managed almost exclusively as trophy species throughout their ranges, embody this controversy, which has led to polarizing views among scientists and stakeholders as to how mountain sheep should be managed. Our goal in this commentary was to discuss the relative contributions of the key ecological and intrinsic factors that influence horn growth, how those factors might interact with harvest strategies, and identify what determinants of horn size are most amenable to management and most effective in achieving desired outcomes. Despite repeated results demonstrating that age or nutrition frequently override genetic contributions to size of horns, attention has been given to the role of genetics and its relationship to harvest of mountain sheep. Given the hyperbole surrounding trophy management and big horns, we suggest the importance of females in the management of mountain sheep has been largely forgotten. Maternal condition can instigate life-long effects on size and growth of males (via maternal effects), and abundance of females, in turn, affects nutritional limitation within populations through density-dependent feedbacks. If production of males with large horns is an objective, we contend that management programs should, integrate monitoring of nutritional status of populations, and where evidence indicates nutritional limitation through density dependence, seek to regulate abundance and per capita nutrition via harvest of females. We propose that extrinsic regulation (i.e., removal by harvest or translocation) is the most effective way to manage per capita availability of forage resources and, thus, nutritional limitation on growth of males. Not only can female harvest improve growth in body size and horns of males through enhanced nutrition of growing males and their mothers, such management also 1) may yield a nutritional buffer against environmental stochasticity and erratic population fluctuations, 2) be employed in areas where other management alternatives such as habitat manipulation may not be feasible, 3) may reduce frequency or magnitude of epizootic die-offs, and 4) will increase hunter opportunity and involvement in management. Ultimately, we call for greater recognition of the pervasive role of the ewe, and other female ungulat...

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Forage quality's influence on mule deer fawns

Cited by 42 publications

References 35 publications

Combined effects of long‐term feeding, population density and vegetation green‐up on reindeer demography

Combined effects of long‐term feeding, population density and vegetation green‐up on reindeer demography

NDVI exhibits mixed success in predicting spatiotemporal variation in caribou summer forage quality and quantity

Horn size and nutrition in mountain sheep: Can ewe handle the truth?

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