College of Letters & Science

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The College of Letters and Science, the largest center for learning, teaching and research at Montana State University, offers students an excellent liberal arts and sciences education in nearly 50 majors, 25 minors and over 25 graduate degrees within the four areas of the humanities, natural sciences, mathematics and social sciences.

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Effects of de-snaring on the demography and population dynamics of African lions
(Elsevier BV, 2023-10) Banda, Kambwiri; Creel, Scott; Sichande, Mwamba; Mweetwa, Thandiwe; Mwape, Henry; Reyes de Merkle, Johnathan; Mwansa Bwalya, Lengwe; Simpamba, Twakundine; McRobb, Rachel; Becker, Matthew S.
Lions and other African large carnivores are in decline, due in part to effects of illegal hunting with snares, which can reduce prey availability and directly kill or injure carnivores. It is difficult to effectively remove snares from large ecosystems by patrolling, but an additional approach to reduce effects on large carnivores is to monitor the population closely and de-snare individuals who are found in a snare or have broken free but still carry the wire (often with serious injury). The effectiveness of de-snaring programs to reduce impacts on large carnivores has not been directly tested. Here, we used long-term demographic data from 386 individually identified lions in the Luangwa Valley Ecosystem to test the effects on population growth (λ) and population size (N) of a program to remove snares from injured lions and treat their wounds. Stochastic Leslie matrix projections for a period of five years showed that the population grew with the benefits of de-snaring, but was expected to decline without de-snaring. Mean annual growth (λ) with de-snaring was 1.037 (with growth in 70% of years), closely matching observed changes in population size. Mean annual growth was 0.99 (with growth in 47% of years) for a model that assumed snared animals would have died if not treated, and 0.95 (with growth in 37% of years) for models that also accounted for super-additive effects via the death of dependent cubs and increased infanticide with increased male mortality. De-snaring requires intensive effort, but it can appreciably reduce the effect of snaring on lion population dynamics.
Predation strongly limits demography of a keystone migratory herbivore in a recovering transfrontier ecosystem
(Wiley, 2022-10) Watson, Fred; Becker, Matthew S.; Smit, Daan; Droge, Egil; Mukula, Teddy; Martens, Sandra; Mwaba, Shadrach; Christianson, David; Creel, Scott; Brennan, Angela; M'soka, Jassiel; Gaylard, Angela; Simukonda, Chuma; Nyirenda, Moses; Mayani, Bridget
Large herbivore migrations are imperiled globally; however the factors limiting a population across its migratory range are typically poorly understood. Zambia's Greater Liuwa Ecosystem (GLE) contains one of the largest remaining blue wildebeest (Connochaetes taurinus taurinus) migrations, yet the population structure, vital rates, and limiting factors are virtually unknown. We conducted a long-term demographic study of GLE wildebeest from 2012 to 2019 of 107 collared adult females and their calves, 7352 herd observations, 12 aerial population surveys, and concurrent carnivore studies. We applied methods of vital rate estimation and survival analysis within a Bayesian estimation framework. From herd composition observations, we estimated rates of fecundity, first-year survival, and recruitment as 68%, 56%, and 38% respectively, with pronounced interannual variation. Similar rates were estimated from calf-detections with collared cows. Adult survival rates declined steadily from 91% at age 2 years to 61% at age 10 years thereafter dropping more sharply to 2% at age 16 years. Predation, particularly by spotted hyena, was the predominant cause of death for all wildebeest ages and focused on older animals. Starvation only accounted for 0.8% of all unbiased known natural causes of death. Mortality risk differed substantially between wet and dry season ranges, reflecting strong spatio-temporal differences in habitat and predator densities. There was substantial evidence that mortality risk to adults was 27% higher in the wet season, and strong evidence that it was 45% higher in the migratory range where predator density was highest. The estimated vital rates were internally consistent, predicting a stable population trajectory consistent with aerial estimates. From essentially zero knowledge of GLE wildebeest dynamics, this work provides vital rates, age structure, limiting factors, and a plausible mechanism for the migratory tendency, and a robust model-based foundation to evaluate the effects of potential restrictions in migratory range, climate change, predator–prey dynamics, and poaching.
African wild dog movements show contrasting responses to long and short term risk of encountering lions: analysis using dynamic Brownian bridge movement models
(Springer Science and Business Media LLC, 2022-12) Goodheart, Ben; Creel, Scott; Vinks, Milan A.; Banda, Kambwiri; Reyes de Merkle, Johnathan; Kusler, Anna; Dart, Chase; Banda, Kachama; Becker, Matthew S.; Indala, Peter; Simukonda, Chuma; Kaluka, Adrian
Background Prey depletion is a threat to the world’s large carnivores, and is likely to affect subordinate competitors within the large carnivore guild disproportionately. African lions limit African wild dog populations through interference competition and intraguild predation. When lion density is reduced as a result of prey depletion, wild dogs are not competitively released, and their population density remains low. Research examining distributions has demonstrated spatial avoidance of lions by wild dogs, but the effects of lions on patterns of movement have not been tested. Movement is one of the most energetically costly activities for many species and is particularly costly for cursorial hunters like wild dogs. Therefore, testing how top-down, bottom-up, and anthropogenic variables affect movement patterns can provide insight into mechanisms that limit wild dogs (and other subordinate competitors) in resource-depleted ecosystems. Methods We measured movement rates using the motion variance from dynamic Brownian Bridge Movement Models (dBBMMs) fit to data from GPS-collared wild dogs, then used a generalized linear model to test for effects on movement of predation risk from lions, predictors of prey density, and anthropogenic and seasonal variables. Results Wild dogs proactively reduced movement in areas with high lion density, but reactively increased movement when lions were immediately nearby. Predictors of prey density had consistently weaker effects on movement than lions did, but movements were reduced in the wet season and when dependent offspring were present. Conclusion Wild dogs alter their patterns of movement in response to lions in ways that are likely to have important energetic consequences. Our results support the recent suggestion that competitive limitation of wild dogs by lions remains strong in ecosystems where lion and wild dog densities are both low as a result of anthropogenic prey depletion. Our results reinforce an emerging pattern that movements often show contrasting responses to long-term and short-term variation in predation risk.
A retrospective view of early research on dominance, stress and reproduction in cooperatively breeding carnivores
(Elsevier BV, 2022-04) Creel, Scott
Social carnivores have been central in studies of cooperative breeding, and research using noninvasive methods to examine behavioral and endocrine mechanisms of reproductive suppression started in the 1980s with dwarf mongooses in Serengeti National Park. Here, I synthesize the methods, findings and limitations of a research program that examined relationships between social dominance, age, mass, aggression, mating, gonadal steroids, glucocorticoids and reproduction in female and male dwarf mongooses, African wild dogs and wolves. Infanticide is a reliable backstop for reproductive suppression in females, and reproduction is energetically costly in these species. These conditions favor hypothalamic – pituitary – gonadal (HPG) adaptations that reduce the fertility of subordinate females to avoid the cost of producing doomed offspring. Infanticide also favors close synchronization of reproduction when subordinate females do become pregnant. In males, infanticide is a less reliable backstop and reproduction is less costly, so direct effects of subordination on fertility are less pronounced. Age is a strong predictor of social dominance in these species, but the evolutionary reason for this is not clear. In dwarf mongooses and wild dogs, alpha females were never deposed by younger packmates, but alpha males were: this difference is also not understood. Patterns of reproduction supported models predicting that alphas are less likely to share reproduction when the fitness costs of reproduction are high, when the fitness expected for dispersers is low, and with young subordinates to whom they are more closely related. Correlations between dominance and adrenal glucocorticoid concentrations varied between species and sexes, but did not support the hypothesis that chronic stress causes reproductive suppression.
A retrospective view of early research on dominance, stress and reproduction in cooperatively breeding carnivores
(Elsevier BV, 2022-04) Creel, Scott
Social carnivores have been central in studies of cooperative breeding, and research using noninvasive methods to examine behavioral and endocrine mechanisms of reproductive suppression started in the 1980s with dwarf mongooses in Serengeti National Park. Here, I synthesize the methods, ﬁndings and limitations of a research program that examined relationships between social dominance, age, mass, aggression, mating, gonadal steroids, glucocorticoids and reproduction in female and male dwarf mongooses, African wild dogs and wolves. Infanti-cide is a reliable backstop for reproductive suppression in females, and reproduction is energetically costly in these species. These conditions favor hypothalamic – pituitary – gonadal (HPG) adaptations that reduce the fertility of subordinate females to avoid the cost of producing doomed offspring. Infanticide also favors close synchronization of reproduction when subordinate females do become pregnant. In males, infanticide is a less reliable backstop and reproduction is less costly, so direct effects of subordination on fertility are less pro-nounced. Age is a strong predictor of social dominance in these species, but the evolutionary reason for this is not clear. In dwarf mongooses and wild dogs, alpha females were never deposed by younger packmates, but alpha males were: this difference is also not understood. Patterns of reproduction supported models predicting that alphas are less likely to share reproduction when the ﬁtness costs of reproduction are high, when the ﬁtness expected for dispersers is low, and with young subordinates to whom they are more closely related. Correlations between dominance and adrenal glucocorticoid concentrations varied between species and sexes, but did not support the hypothesis that chronic stress causes reproductive suppression.
A retrospective view of early research on dominance, stress and reproduction in cooperatively breeding carnivores
(Elsevier BV, 2022-03) Creel, Scott
Social carnivores have been central in studies of cooperative breeding, and research using noninvasive methods to examine behavioral and endocrine mechanisms of reproductive suppression started in the 1980s with dwarf mongooses in Serengeti National Park. Here, I synthesize the methods, findings and limitations of a research program that examined relationships between social dominance, age, mass, aggression, mating, gonadal steroids, glucocorticoids and reproduction in female and male dwarf mongooses, African wild dogs and wolves. Infanticide is a reliable backstop for reproductive suppression in females, and reproduction is energetically costly in these species. These conditions favor hypothalamic – pituitary – gonadal (HPG) adaptations that reduce the fertility of subordinate females to avoid the cost of producing doomed offspring. Infanticide also favors close synchronization of reproduction when subordinate females do become pregnant. In males, infanticide is a less reliable backstop and reproduction is less costly, so direct effects of subordination on fertility are less pronounced. Age is a strong predictor of social dominance in these species, but the evolutionary reason for this is not clear. In dwarf mongooses and wild dogs, alpha females were never deposed by younger packmates, but alpha males were: this difference is also not understood. Patterns of reproduction supported models predicting that alphas are less likely to share reproduction when the fitness costs of reproduction are high, when the fitness expected for dispersers is low, and with young subordinates to whom they are more closely related. Correlations between dominance and adrenal glucocorticoid concentrations varied between species and sexes, but did not support the hypothesis that chronic stress causes reproductive suppression.
Assessing the Performance of Index Calibration Survey Methods to Monitor Populations of Wide‐ranging Low‐density Carnivores
(2020-03) Droge, Egil; Creel, Scott; Becker, Matthew S.; Loveridge, Andrew J.; Sousa, Lara L.; Macdonald, David W.
Apex carnivores are wide‐ranging, low‐density, hard to detect, and declining throughout most of their range, making population monitoring both critical and challenging. Rapid and inexpensive index calibration survey (ICS) methods have been developed to monitor large African carnivores. ICS methods assume constant detection probability and a predictable relationship between the index and the actual population of interest. The precision and utility of the resulting estimates from ICS methods have been questioned. We assessed the performance of one ICS method for large carnivores—track counts—with data from two long‐term studies of African lion populations. We conducted Monte Carlo simulation of intersections between transects (road segments) and lion movement paths (from GPS collar data) at varying survey intensities. Then, using the track count method we estimated population size and its confidence limits. We found that estimates either overstate precision or are too imprecise to be meaningful. Overstated precision stemmed from discarding the variance from population estimates when developing the method and from treating the conversion from tracks counts to population density as a back‐transformation, rather than applying the equation for the variance of a linear function. To effectively assess the status of species, the IUCN has set guidelines, and these should be integrated in survey designs. We propose reporting the half relative confidence interval width (HRCIW) as an easily calculable and interpretable measure of precision. We show that track counts do not adhere to IUCN criteria, and we argue that ICS methods for wide‐ranging low‐density species are unlikely to meet those criteria. Established, intensive methods lead to precise estimates, but some new approaches, like short, intensive, (spatial) capture–mark–recapture (CMR/SECR) studies, aided by camera trapping and/or genetic identification of individuals, hold promise. A handbook of best practices in monitoring populations of apex carnivores is strongly recommended.
Carnivores, competition and genetic connectivity in the Anthropocene
(2019-11) Creel, Scott; Spong, Goran; Becker, Matthew S.; Simukonda, Chuma; Norman, Anita; Schiffthaler, Bastian; Chifunte, Clive
Current extinction rates are comparable to five prior mass extinctions in the earth’s history, and are strongly affected by human activities that have modified more than half of the earth’s terrestrial surface. Increasing human activity restricts animal movements and isolates formerly connected populations, a particular concern for the conservation of large carnivores, but no prior research has used high throughput sequencing in a standardized manner to examine genetic connectivity for multiple species of large carnivores and multiple ecosystems. Here, we used RAD SNP genotypes to test for differences in connectivity between multiple ecosystems for African wild dogs (Lycaon pictus) and lions (Panthera leo), and to test correlations between genetic distance, geographic distance and landscape resistance due to human activity. We found weaker connectivity, a stronger correlation between genetic distance and geographic distance, and a stronger correlation between genetic distance and landscape resistance for lions than for wild dogs, and propose a new hypothesis that adaptations to interspecific competition may help to explain differences in vulnerability to isolation by humans.
Foraging investment in a long-lived herbivore and vulnerability to coursing and stalking predators
(2018-10) Christianson, David A.; Becker, Matthew S.; Brennan, Angela; Creel, Scott; Droge, Egil; M'soka, Jassiel; Mukula, Teddy; Schuette, Paul; Smit, Daan; Watson, Fred
Allocating resources to growth and reproduction requires grazers to invest time in foraging, but foraging promotes dental senescence and constrains expression of proactive antipredator behaviors such as vigilance. We explored the relationship between carnivore prey selection and prey foraging effort using incisors collected from the kills of coursing and stalking carnivores. We predicted that prey investing less effort in foraging would be killed more frequently by coursers, predators that often exploit physical deficiencies. However, such prey could expect delayed dental senescence. We predicted that individuals investing more effort in foraging would be killed more frequently by stalkers, predators that often exploit behavioral vulnerabilities. Further these prey could expect earlier dental senescence. We tested these predictions by comparing variation in age-corrected tooth wear, a proxy of cumulative foraging effort, in adult (3.4-11.9 years) wildebeest killed by coursing and stalking carnivores. Predator type was a strong predictor of age-corrected tooth wear within each gender. We found greater foraging effort and earlier expected dental senescence, equivalent to 2.6 additional years of foraging, in female wildebeest killed by stalkers than in females killed by coursers. However, male wildebeest showed the opposite pattern with the equivalent of 2.4 years of additional tooth wear in males killed by coursers as compared to those killed by stalkers. Sex-specific variation in the effects of foraging effort on vulnerability was unexpected and suggests that behavioral and physical aspects of vulnerability may not be subject to the same selective pressures across genders in multipredator landscapes.
Quantifying lion (Panthera leo) demographic response following a three-year moratorium on trophy hunting.
(2018-05) Mweetwa, Thandiwe; Christianson, David A.; Becker, Matthew S.; Creel, Scott; Rosenblatt, Elias G.; Merkle, Johnathan; Droge, Egil; Mwape, Henry; Masonde, Jones; Simpamba, Twakundine
Factors that limit African lion populations are manifold and well-recognized, but their relative demographic effects remain poorly understood, particularly trophy hunting near protected areas. We identified and monitored 386 individual lions within and around South Luangwa National Park, Zambia, for five years (2008-2012) with trophy hunting and for three additional years (2013-2015) during a hunting moratorium. We used these data with mark-resight models to estimate the effects of hunting on lion survival, recruitment, and abundance. The best survival models, accounting for imperfect detection, revealed strong positive effects of the moratorium, with survival increasing by 17.1 and 14.0 percentage points in subadult and adult males, respectively. Smaller effects on adult female survival and positive effects on cub survival were also detected. The sex-ratio of cubs shifted from unbiased during trophy-hunting to female-biased during the moratorium. Closed mark-recapture models revealed a large increase in lion abundance during the hunting moratorium, from 116 lions in 2012 immediately preceding the moratorium to 209 lions in the last year of the moratorium. More cubs were produced each year of the moratorium than in any year with trophy hunting. Lion demographics shifted from a male-depleted population consisting mostly of adult (â‰¥4 years) females to a younger population with more (>29%) adult males. These data show that the three-year moratorium was effective at growing the Luangwa lion population and increasing the number of adult males. The results suggest that moratoria may be an effective tool for improving the sustainability of lion trophy hunting, particularly where systematic monitoring, conservative quotas, and age-based harvesting are difficult to enforce.

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