Black bear management in Louisiana is focused on conservation and development of habitat required by black bears and the reduction of human/bear conflicts. Research is directed at gathering of data to assess and monitor bear populations, productivity, population viability and public opinion regarding bears and bear management.
Habitat Management and Restoration
Habitat loss was one of the primary reasons black bears were listed as a threatened species in 1992. Following the Mississippi River flood of 1927, a massive flood control effort was launched which resulted in much of the upper Mississippi River floodplain of Louisiana being protected from flooding by U.S. Army Corps of Engineers levees. The resulting reduction in flooding, coupled with technology made the fertile soils of the upper Mississippi River floodplain desirable for agriculture. In addition, high soybean prices accelerated conversion of forestland to agriculture in the 1960s and 1970s. Conservation provisions in the federal Farm Bill slowed forestland conversion by the mid-1980’s. However, by then only about 20% of the landscape remained forested.
A number of programs and initiatives have resulted in the conservation and restoration of over 600,000 acres of forestland in the Mississippi River floodplain of Louisiana. The Louisiana Department of Wildlife and Fisheries and the U.S. Fish and Wildlife Service have conserved land through acquisition of Wildlife Management Areas and National Wildlife Refuges. Forestland on private property has been restored through U.S.D.A. programs such as the Wetlands Reserve Program and Conservation Reserve Program as well as through programs of private conservation organizations such as the Black Bear Conservation Coalition, The Nature Conservancy and Ducks Unlimited.
It is not enough to just restore forestland. For maximum benefit to bears and other wildlife, it must also be managed properly. Wildlife habitat management assistance is provided to landowners through a number of state, federal and private programs. One such program is the Louisiana Department of Wildlife and Fisheries’ Technical Services Program. Through this program, department biologists work with landowners to provide guidance to improve wildlife habitat on their property.
An important component of bear management involves educational efforts to reduce bear – human conflicts. Bears are intelligent and adaptable animals that will take advantage of sources of food that are made available to them as a result of human activity. Unsecured garbage and wildlife feeders are two common causes of bear – human conflict. The department works to educate and inform the public about living around bears through brochures, public meetings, teacher workshops, outreach events, hunter education classes and technical assistance to individuals experiencing problems.
The department and its partners have been conducting extensive research on black bears for several years. This research is being conducted to gather information on populations, productivity, and population viability to determine if the criteria for removing the LBB from the list of threatened species have been met and to gather information needed to properly manage LBB populations to ensure they remain a viable part of Louisiana’s wildlife community.
“Population Viability and Connectivity of the Louisiana Black Bear (Ursus americanus luteolus)”
In 1992, the U.S. Fish and Wildlife Service (USFWS) granted Ursus americanus luteolus (Louisiana black bear) threatened status under the U.S. Endangered Species Act of 1973, listing loss and fragmentation of habitat as the primary threats. A study was developed by the U.S. Geological Survey in cooperation with the University of Tennessee, the Louisiana Department of Wildlife and Fisheries, and the USFWS to estimate demographic rates and genetic structure of Louisiana black bear populations; evaluate relations between environmental and anthropogenic factors and demographic, genetic, and movement characteristics of Louisiana black bear populations; and develop data-driven stochastic population projection models to assess long-term persistence of individual subpopulations and the overall black bear population in Louisiana.
Data were collected with non-invasive DNA sampling, live capture, winter den visits, and radio monitoring from 2002 to 2012 in the four areas supporting breeding subpopulations in Louisiana: Tensas River Basin (TRB), Upper Atchafalaya River Basin (UARB), Lower Atchafalaya River Basin (LARB), and Three Rivers Complex (TRC). Bears were live trapped and radio collared in the TRB and TRC to estimate survival and reproductive rates, deterministic matrix models were used to estimate asymptotic growth rates, and stochastic population models were used to estimate long-term viability. DNA extracted from hair collected at baited, barbed-wire enclosures in the TRB, UARB, and LARB and capture-mark-recapture (CMR) analysis based on Bayesian hierarchical modeling methods were used to estimate apparent survival (ϕ), per capita recruitment (γ), abundance (N), realized growth rate (λ), and long-term viability.
From 2002 to 2012, we radio monitored 86 adult females greater than (>) 2 years old within the TRB, and 43 adult females were monitored in the TRC. The mean annual survival rate estimate ranged from 0.97 to 0.99 for the TRB and from 0.93 to 0.97 for the TRC. Fecundity and yearling recruitment in the TRB were 0.47 and 0.15, respectively, whereas estimates for the TRC were 0.37 and 0.18. Depending on estimated carrying capacity, the strength of the density dependence, level of uncertainty, and the treatment of unresolved signals, persistence probabilities for the TRC subpopulation ranged from 0.295 to 0.999.
Estimates of N for females in the TRB ranged from 140 to 163 during 2006–12 when detection heterogeneity was assumed to follow a logistic-normal distribution (Model 1) and from 133 to 158 when a 2-point finite mixture distribution was assumed (Model 2). Annual estimates of γ ranged from 0.00 to 0.16 and from 0.00 to 0.22, depending on the model, and estimates of ϕ 2 ranged from 0.87 to 0.93 during that period. In the UARB, estimates of N for females ranged from 25 to 44 during the study period, regardless of heterogeneity model. Estimated γ ranged from 0.00 to 0.41, and ϕ ranged from 0.88 to 0.90 during that period. Estimated N for females in the LARB ranged from 78 to 97 from 2010 to 2012 based on Model 1 and from 68 to 84 based on Model 2. Estimates of γ were 0.00 for 2010–11 regardless of heterogeneity model and ranged from 0.24 to 0.31 for 2011–12, depending on the model assumptions. We estimated ϕ as 0.81 for 2010–11, and from 0.84 to 0.85 for 2011–12, depending on model assumptions.
On the basis of vital rate estimates from Model 1 of the CMR analysis, probability of persistence over 100 years for the TRB subpopulation was >0.999, 0.975, and 0.958 for process-only, 50-percent (%) credible interval (CI), and 95% CI projections, respectively. Similarly, the probability of persistence based on Model 2 was >0.999, 0.982, and 0.958. For the UARB, probabilities of persistence based on Model 1 were >0.999, 0.971, and 0.958 for process-only, 50% CI, and 95% CI projections, respectively, and 0.993, 0.929, and 0.849 for Model 2. Using the telemetry and reproductive data from the TRC, probabilities of persistence were greater than or equal to 0.95 only for projections based on the most optimistic set of assumptions. Assuming that the dynamics of the TRB, TRC, and UARB subpopulations were independent and using the most pessimistic population-specific persistence probabilities (that is, 0.958, 0.295, and 0.849, respectively), the probability of persistence for bears in the overall population system was 0.996.
Genetic methods were used to estimate interchange and structure between subpopulations in Louisiana and in Minnesota (MINN); Mississippi (MISS); and the White River Basin (WRB), Arkansas. Results from the all-population and the WRB–TRB clustering analyses indicate at least five genetically distinct subpopulations. The genetic clustering and migrant analyses combined with capture data provided direct evidence that interchange had occurred from the WRB to the TRB and MISS, from the TRB to MISS, from the UARB to the TRC, and from the TRC to the TRB. Indirect evidence that interchange occurred from the UARB to the TRC and from the UARB to the TRB by way of the TRC was documented. No evidence was found of interchange from any of the subpopulations to the WRB, UARB, or LARB.
From April 2010 to April 2012, global positioning system (GPS) radio collars were placed on 8 female and 23 male bears ranging from 1 to 11 years of age to develop a step-selection function model to predict routes and rates of interchange. For both males and females, the probability of a step being selected increased as the distance to natural land cover and agriculture at the end of the step decreased and as distance from roads at the end of a step increased. Of 4,000 correlated random walks, the least potential interchange was between TRB and TRC and between UARB and LARB, but the relative potential for natural interchange between UARB and TRC was high. The step-selection model predicted that dispersals between the LARB and UARB subpopulations were infrequent but possible for males and nearly nonexistent for females. No evidence of natural female dispersal between subpopulations has been documented thus far, which is also consistent with model predictions. Both the genetic data and the step-selection results illustrated the value of the reintroduced TRC subpopulation in facilitating connectivity.
By Jared S. Laufenberg and Joseph D. Clark [Open-File Report 2014-1228]
“Estimating Population Parameters of the Louisiana Black Bear in the Tensas River Basin, Louisiana, Using Robust Design Capture-Mark-Recapture.”
The Louisiana black bear (Ursus americanus luteolus) is listed as a threatened species under the protection of the Endangered Species Act of 1973. The Louisiana Black Bear Recovery Plan calls for research regarding bear population viability and biology. From July 2006 to August 2008 I conducted a 3-year robust design capture-mark-recapture study of bears in the Tensas River Basin of northeast Louisiana. I used microsatellite genotypes from DNA extracted from hair samples to identify individual bears.
Robust design encounter histories of bears were analyzed using Huggins full heterogeneity models in Program MARK. I ranked models using Akaike’s Information Criterion (AIC). I used model averaging to account for model selection uncertainty.
Apparent survival rate, temporary emigration, the probability of an individual coming from 1 of 2 mixtures, and the probability of capture and recapture were estimated from encounter histories. Population abundance was a derived parameter.
I used abundance estimates to calculate density, and population growth. Apparent survival did not differ by gender or year and was 0.91 (95% CI = 0.62–0.98). There was no temporary emigration. Models in which capture probabilities varied by mixtures were favored over models lacking mixtures. For both genders and across all years, >80% of individuals were in a mixture with capture probabilities ranging from 0.02 to 0.03 for males and 0.07 to 0.08 for females.
Estimates for recapture were higher than capture indicating a positive behavioral response to being captured for females. Model-averaged estimates of abundance for females were 143 (95% CI = 113–204), 106 (95% CI = 83–151), and 133 (95% CI = 100–195) and for males were 198 (95% CI = 117–360), 116 (95% CI = 69–209), and 185 (95% CI = 112–323) during 2006, 2007 and 2008, respectively.
Mean population size for both genders averaged across years was 294 (SE = 31) and density was 0.66 bears/km2 (SE = 0.07). Video and photographic evidence suggested that adult males were less likely to be sampled while visiting hair snares. I offer suggestions to reduce this heterogeneity bias.
“Estimating Population Parameters of the Louisiana Black Bear in the Upper Atchafalaya River Basin.”
In 1992, the Louisiana black bear (Ursus americanus luteolus) was granted threatened status under the Endangered Species Act primarily because of extensive habitat loss and fragmentation.
Currently, the Louisiana black bear is restricted to 3 relatively small, disjunct breeding subpopulations located in the Tensas River Basin of northeast Louisiana, the upper Atchafalaya River Basin (ARB) of south-central Louisiana, and coastal Louisiana. The 1995 Recovery Plan mandates research to determine the viability of the remaining subpopulations.
I conducted a capture-mark-recapture study during 2007–2009 to estimate population parameters for the ARB bear subpopulation by collecting hair samples (n = 2,977) from 115 barbed-wire hair traps during 8 1-week periods each summer. DNA was extracted from those hair samples and microsatellite genotypes were used to identify individuals. I analyzed encounter histories using the Huggins full heterogeneity estimator in a robust design framework in Program MARK.
I compared candidate models incorporating heterogeneity, behavior, and time effects on capture using information-theoretic methods. I directly estimated apparent survival, temporary emigration, probability of capture and recapture, and probability of belonging to 1 of 2 mixtures; population abundance was a derived parameter. Apparent survival was 0.91 (SE = 0.06) and did not vary by gender or year.
There was some evidence of temporary emigration for males only (0.10, 95% CI = 0.001–0.900). I modeled capture probabilities with a 2-mixture distribution for both male and females. Overall mean weekly capture probability was 0.12 (SE = 0.03) and 0.25 (SE = 0.04) for males and females, respectively. Recapture rates indicated a positive behavioral response to capture.
Model-averaged mean annual abundance was 56 (SE = 4.5, 95% CI = 49–68). I calculated population density using spatially-explicit maximum-likelihood methods; model averaged density was 0.15 bears/km2 (SE = 0.03). My results updated previous abundance estimates for the ARB bear subpopulation and will be used in a population viability analysis to determine if recovery criteria for the Louisiana black bear have been met.
“ POPULATION DEMOGRAPHICS AND GENETIC STRUCTURE OF BLACK BEARS IN COASTAL LOUISIANA”
The range and abundance of the Louisiana black bear (Ursus americanus luteolus) were greatly diminished during the 20th century. This subspecies was reduced to 3 small, isolated subpopulations in Louisiana as bottomland hardwood habitat was converted to agriculture. These bears were listed as threatened by the U.S. Fish and Wildlife Service in 1992 and a recovery plan was published in 1995. Recovery requires estimates of population parameters to evaluate current population status and future viability. I conducted a mark-recapture study from 2010 to 2012 to estimate demographic parameters of the coastal population of Louisiana black bears. Because inbreeding is a concern for small, isolated populations, I analyzed 23 microsatellite loci to investigate genetic structure and migration rates within the coastal population and between the coastal and other regional populations. Using non-invasive methods, I collected 3,698 hair samples during 3 summers and used DNA to identify 190 individuals. I analyzed encounter histories using Robust Design, a combination of open and closed mark-recapture models, with the full closed captures with heterogeneity model in Program MARK. I estimated density using spatially explicit capture-recapture. I used Akaike’s Information Criterion (AIC) to rank models and averaged across years according to AIC weight. The model-averaged abundance estimate for females was 77 (95% CI = 66–89) and for males was 61 (95% CI = 53–69). Population growth rate was negative from 2010 to 2011, positive from 2011 to 2012, and averaged 1.08. Apparent survival ranged from 0.83 to 0.89 depending on sex and year. Population density was 0.35 bears/km2 (95% CI = 0.30–0.41). Principal Coordinate Analysis and assignment tests revealed 2 genetic clusters within the population. Migration rates were male biased and higher than expected based on genetic structure. The population appears to be recovering from past fragmentation but evidence for a bottleneck was inconclusive. I conclude that genetic isolation and inbreeding within the coastal population pose less danger than isolation and demographic threats. My results will ultimately be used as part of a population viability analysis to estimate the sustainability of the Louisiana black bear population.