Robert G. Wright

Survival of wild turkey hens in Southwestern Wisconsin

Successful restoration of wild turkeys (Meleagris gallopavo) to Wisconsin has stimulated increased interest in hunting and a need for specific management information. We determined survival and causes of mortality for 224 radiomarked hens during 1988-94 in Vernon County, Wisconsin under a relatively liberal fall harvest regime. Annual survival ranged from 43.1 to 66.0 and averaged 52.7% (SE = 4.8). Seasonal survival averaged 72.2 (SE = 2.9), 81.3 (SE = 3.3), and 89.3% (SE = 2.5) during recruitment (16 Mar to 14 Jul), post-recruitment (15 Jul to 21 Nov), and winter (22 Nov to 15 Mar), and was lower (P = 0.001) during recruitment than during winter. Predation accounted for 71.2% of all deaths and was highest during recruitment. Localized starvation occurred during a winter with 49 consecutive days of deep snow and cold temperatures. Cumulative fall hunter densities were about 3.5/km 2 of woodland and the fall harvest rate of radioed hens averaged 7.3%. Turkey densities declined during the study and more conservative fall harvests may be necessary.

Reproductive ecology of eastern wild turkeys in southwestern Wisconsin

Developing sound harvest strategies for wild turkey populations requires geographically specific information on population dynamics. The absence of this information prompted us to investigate the reproductive ecology of a hunted population of eastern wild turkeys (Meleagris gallopavo silvestris) in southwestern Wisconsin during 1989-92. Nesting rates averaged 0.927 and were higher for adults than subadults (P = 0.003, n = 220). No age-specific differences were detected for renesting rates (P = 0.413, n = 147), nest success for first (P = 0.549, n = 199) or second (P = 0.685, n = 81) attempts, mean clutch size (P = 0.300, n = 37), or mean number of eggs hatched (P = 0.304, n = 24). Hen success averaged 0.217 (n = 212). Hen success was higher for adults than subadults (P = 0.047) and did not vary among years (P = 0.254). Mammalian predation was the primary factor affecting reproductive success. The level of recruitment during the study was inadequate to maintain the population.

Wild turkey population dynamics in southwestern Wisconsin

We studied the population dynamics of eastern wild turkeys (Meleagris gallopavo silvestris) in southwestern Wisconsin during 1987-94 to better understand the effects of variation in reproduction and fall harvest on growth of a northern population. We combined yearly estimates of reproduction, survival, and population size in a stochastic population model to estimate the finite rate of increase of the population. Our model indicated recruitment during 1989-92 was inadequate to offset observed mortality: the finite rate of increase was 0.831 ± 0.097 (x ± SE). The simulated trend was corroborated by declines in spring harvest success and observations of turkeys by deer hunters. We illustrate that population growth is affected by variation in both reproduction and fall harvest rates. The population decline was apparently caused by reduced recruitment in combination with reduced hen survival associated with initiation of fall hunting. The decline in recruitment was associated with cold and wet spring weather (r 2 = 0.92, P < 0.001). Analysis of 103 years of weather data suggested the low level of recruitment observed during 1989-92 may be representative of the long-term recruitment potential of this population. More conservative harvest strategies may be appropriate for northern populations.

Relative importance of phosphorus, fish biomass, and watershed land use as drivers of phytoplankton abundance in shallow lakes

Phytoplankton abundance in shallow lakes is potentially influenced by ambient phosphorus concentrations, nutrient loading accentuated by human activities in lake watersheds, and abundance of planktivorous and benthivorous fish. However, few studies have simultaneously assessed the relative importance of these factors influencing phytoplankton abundance over large spatial scales. We assessed relative influences of watershed characteristics, total phosphorus concentrations, and fish biomass on phytoplankton abundance in 70 shallow lakes in western Minnesota (USA) during summer 2005 and 2006. Our independent variables included total phosphorus (TP), benthivore biomass, planktivore biomass, summed planktivore and benthivore biomass (summed fish), areal extent of agriculture in the watershed, region (prairie versus parkland lakes), and year. Predictive models containing from one to three independent variables were compared using an information theoretic approach. The most parsimonious model consisted of TP and summed fish, and had over 10,000-fold greater support compared to models using just TP or summed fish, or models comprised of other variables. We also found no evidence that relative importance of predictor variables differed between regions or years, and parameter estimates of TP and summed fish were temporally and spatially consistent. TP and summed fish were only weakly correlated, and the model using both variables was a large improvement over using either variable alone. This indicates these two variables can independently increase phytoplankton abundance, which emphasizes the importance of managing both nutrients and fish when trying to control phytoplankton abundance in shallow lakes.

Comparing Effects of Lake- and Watershed-Scale Influences on Communities of Aquatic Invertebrates in Shallow Lakes

Constraints on lake communities are complex and are usually studied by using limited combinations of variables derived from measurements within or adjacent to study waters. While informative, results often provide limited insight about magnitude of simultaneous influences operating at multiple scales, such as lake- vs. watershed-scale. To formulate comparisons of such contrasting influences, we explored factors controlling the abundance of predominant aquatic invertebrates in 75 shallow lakes in western Minnesota, USA. Using robust regression techniques, we modeled relative abundance of Amphipoda, small and large cladocera, Corixidae, aquatic Diptera, and an aggregate taxon that combined Ephemeroptera-Trichoptera-Odonata (ETO) in response to lake- and watershed-scale characteristics. Predictor variables included fish and submerged plant abundance, linear distance to the nearest wetland or lake, watershed size, and proportion of the watershed in agricultural production. Among-lake variability in invertebrate abundance was more often explained by lake-scale predictors than by variables based on watershed characteristics. For example, we identified significant associations between fish presence and community type and abundance of small and large cladocera, Amphipoda, Diptera, and ETO. Abundance of Amphipoda, Diptera, and Corixidae were also positively correlated with submerged plant abundance. We observed no associations between lake-watershed variables and abundance of our invertebrate taxa. Broadly, our results seem to indicate preeminence of lake-level influences on aquatic invertebrates in shallow lakes, but historical land-use legacies may mask important relationships.

Monitoring movement behavior enhances recognition and understanding of capture-induced abandonment of moose neonates

Capturing and collaring mammalian newborns is a valued technique in studies focused on survival, cause-specific mortality, maternal investment, and other aspects of animal behavior and ecology. Abandonment of ungulate neonates has been highly variable and often may be underestimated due to limited understanding of this maternal behavior. In a study of survival and cause-specific mortality of GPS-collared moose (Alces americanus) calves in a declining population in northeastern Minnesota, 9 of 49 (18.4%) neonates (25 females and 24 males) were abandoned postcapture (8–17 May 2013) by 7 of 31 (22.6%) mothers. During the 1–6-h-interval postcapture, nonabandoning and abandoning mothers were similar distances from their calves. However, for nonabandoning mothers, from 13 to 48 h postcapture mean 6-h-interval distances to their calves steadily approached 0 m, whereas for abandoning mothers, mean distances to their calves continued to increase from 7 to 48 h. Five of the 7 abandoning mothers stayed with their calves immediately after capture for up to 11 h before leaving. Additionally, 5 abandoning mothers and 5 that did not abandon returned a mean 1.4 and 1.3 times, respectively, but abandoning mothers were notably farther from their calves just 1 h prior to returning than nonabandoning mothers. There were no differences in birth date, capture date, bonding or handling times, metrics of body size, or rectal temperature of neonates abandoned versus not abandoned, or in mean age of their mothers. Our study improves understanding of capture-induced abandonment and postcapture behavior of mothers that abandoned and mothers that did not. Employment of GPS collars and associated monitoring technology will continue to enhance our recognition and understanding of human-induced abandonment as it occurs for many species, allow rapid mortality investigations, limiting introduction of biases into analyses due to inaccurate data, and should help to minimize the occurrence of human-induced abandonment.

Fish Influences on Amphibian Presence and Abundance in Prairie and Parkland Landscapes of Minnesota, USA

Abstract Many amphibian populations are declining, and increased understanding of the drivers of amphibian presence and abundance will help in their conservation. In 2005 and 2006 we estimated relative abundance of larvae of two common amphibian taxa, Tiger Salamanders (Ambystoma tigrinum) and ranid tadpoles (Northern Leopard Frog Lithobates pipiens and Wood Frog Lithobates sylvaticus), in 75 shallow lakes in prairie and parkland areas in Minnesota. We used a two-step procedure in which we first modeled presence-absence with data from all lakes and then modeled abundance only in lakes where the amphibian taxa were present. For the two amphibian taxa, a generalized linear mixed effects model was used to examine the effects of dynamic factors like fish abundance and static (timeframe of study) variables like fish community type, depth, and adjacent land cover. Fish variables had the greatest influence but differed for the presence and abundance models. Salamander and tadpole presence was inversely correlated to the abundance of benthivorous fish, while salamander abundance was best explained by total fish abundance and tadpole abundance by fish community type. We did not detect influences of land cover types on the amphibian taxa we surveyed. Our findings are important because they complement previous studies documenting that negative correlations with fish extend beyond piscivores to include both planktivores and benthivores. Hydrological changes in our study landscape (e.g., installation of drainage networks, wetland consolidation) associated with agriculture and other land uses have likely increased the distribution and abundance of fish populations, thus dampening amphibian breeding success.

Cost and Precision Functions for Aerial Quadrat Surveys: a Case Study of Ring-Necked Ducks in Minnesota

Abstract Cost considerations may be as important as precision when making survey-design choices, and the ability to accurately estimate survey costs will be essential if survey budgets become more constrained. We used data from a survey of ring-necked ducks (Aythya collaris) to illustrate how simple distance formulas can be used to construct a cost function for aerial quadrat surveys. Our cost function provided reasonable estimates of effort (hr) and costs, and allowed us to evaluate plot-size choices in terms of expected cost-precision tradeoffs. Although factors influencing costs in wildlife surveys can be complicated, we believe that cost functions deserve more attention and should be routinely considered in conjunction with traditional power analyses.