Increasing Group Size Research Articles

Michener's group-size paradox in cooperatively breeding birds.

According to Michener's paradox, most altruistic groups in nature should be small and large groups should not exist. This is because per capita productivity is thought to decrease as groups get larger, meaning that the share of indirect fitness available to each group member declines, which favours dispersal. The empirical evidence for a decrease in per capita productivity is contradictory, however, and limited to the social Hymenoptera. I report that per capita reproductive success decreased with increasing group size across 26 cooperatively breeding bird species. Small groups comprising two or three individuals were the most common (79% of 16,101 groups), and these had the highest per capita reproductive success. This close fit between per capita reproductive success and the distribution of group sizes in nature suggests that it may indeed be difficult for large groups to evolve through indirect fitness benefits alone.

Social attributes shape antipredator behavior strategies in the ruddy ground-dove

The cost-benefit of social behavior depends on group size and the social interaction. As group size increases, competition for resources increases, while individual vigilance may decrease due to the lower probability of individual predation or increased competition for resources. To test predictions of the “many eyes hypothesis” and the “competition hypothesis”, we investigated the effects of social attributes on the vigilance, foraging, direct conflict and sex on social groups of ruddy ground-doves (Columbina talpacoti) in an urban area. We observed that the number of conspecifics did not influence individual foraging behavior, instead, the vigilance decreased as flock size increased. Moreover, the number of conflicts within the flock negatively affected individual vigilance. However, larger flocks exhibited more direct conflicts, and males were more frequently involved in social conflicts, regardless of the sex ratio of the flock. Finally, the investment in both vigilance and foraging was not influenced by the sex of the focal individual or the sex ratio of the flock. Our findings indicate that conspecific numbers and flock social organization significantly influence the cost-benefit dynamics of flocking behavior. Larger flocks enhance vigilance for predator detection but come at an individual cost due to increased resource competition and conflicts.

Rent dissipation and streamlined costs: Laboratory experiments

The effect of group size and effort cost on rent dissipation in the standard Tullock rent seeking model is examined using a laboratory experiment. Data support qualitative comparative static Nash equilibrium predictions as reductions in both group size and effort cost increase effort levels. However, effort and dissipation rates are above Nash predictions for all treatments. In addition, while cutting per-unit effort costs in half increases individual effort levels, they do not fully double as predicted and therefore lower rent dissipation, creating a policy-relevant “streamlining effect”. A quantal response equilibrium, which adds stochastic elements into the game structure, predicts the observed higher effort levels and dissipation but is proven to be unable to explain the streamlining effect. A modification of quantal response that incorporates implementation error noise and loss aversion outperforms other estimated models and tracks the observed all data patterns more closely, including the streamlining effect.

Disbandment rules that most facilitate the evolution of cooperation

Cooperation is considered a mysterious phenomenon from the perspective of adaptive evolution. However, if an individual can separate from an unsatisfactory group and join another, then this can facilitate positive assortment between cooperative types and promote the evolution of cooperation. What kind of disbandment rule most facilitates the evolution of cooperation? A previous study investigated exogenous disbandment rules and showed that, when games are played between two players, a rule where heterogeneous groups disband facilitates the evolution of cooperation. However, in groups of more than two individuals, a rule strictly requiring homogeneity applied if and only if the expected number of rounds played in a group was greater than some critical value. How large is the critical value? In this study, we make a mathematical analysis using evolutionary game theory. Our results show that the critical number of rounds increases greatly as the group size increases. Consequently, for species with large group sizes, e.g., Homo sapiens, under plausible parameter values, the strict homogeneity rule is unlikely to facilitate the evolution of cooperation. We find instead that a disbandment rule that requires a threshold level of homogeneity outperformed the strict homogeneity rule. Furthermore, we calculate the position of internal equilibria at which cooperators and defectors coexist and show that the initial evolution of cooperation is most encouraged when cooperators are tolerant (intolerant) of defectors if the benefit-to-cost ratio is large (small).

Opposing Responses to Scarcity Emerge from Functionally Unique Sociality Drivers.

AbstractFrom biofilms to whale pods, organisms across taxa live in groups, thereby accruing numerous diverse benefits of sociality. All social organisms, however, pay the inherent cost of increased resource competition. One expects that when resources become scarce, this cost will increase, causing group sizes to decrease. Indeed, this occurs in some species, but there are also species for which group sizes remain stable or even increase under scarcity. What accounts for these opposing responses? We present a conceptual framework, literature review, and theoretical model demonstrating that differing responses to sudden resource shifts can be explained by which sociality benefit exerts the strongest selection pressure on a particular species. We categorize resource-related benefits of sociality into six functionally distinct classes and model their effect on the survival of individuals foraging in groups under different resource conditions. We find that whether, and to what degree, the optimal group size (or correlates thereof) increases, decreases, or remains constant when resource abundance declines depends strongly on the dominant sociality mechanism. Existing data, although limited, support our model predictions. Overall, we show that across a wide diversity of taxa, differences in how group size shifts in response to resource declines can be driven by differences in the primary benefits of sociality.

Social modulation of oogenesis and egg laying in Drosophila melanogaster.

Being part of a group facilitates cooperation between group members but also creates competition for resources. This is a conundrum for gravid females, whose future offspring benefit from being in a group only if there are enough resources relative to group size. Females may therefore be expected to modulate reproductive output depending on social context. In the fruit fly Drosophila melanogaster, females actively attract conspecifics to lay eggs on the same resources, generating groups in which individuals may cooperate or compete. The genetic tractability of this species allows dissecting the mechanisms underlying physiological adaptation to social context. Here, we show that females produce eggs increasingly faster as group size increases. By laying eggs faster when grouped than when isolated, females reduce competition between offspring and increase offspring survival. In addition, grouped females lay eggs during the day, while isolated females lay them at night. We show that responses to the presence of others requires visual input and that flies from any sex, mating status, or species can trigger these responses. The mechanisms of this modulation of egg laying by group is connected to a lifting of the inhibition of light on oogenesis and egg laying, possibly mediated in part by an increase in juvenile hormone activity. Because modulation of reproduction by social context is a hallmark of animals with higher levels of sociality, our findings in a species considered solitary question the validity of this nomenclature and suggest a widespread and profound influence of social context on reproduction.

Playing the political game: the coevolution of institutions with group size and political inequality.

All societies need to form institutional rules to regulate their social interactions. These specify what actions individuals should take in particular situations, and what sanctions will apply if individuals violate these rules. However, forming these institutional rules involves playing a political game-a process of negotiation between individuals that is costly and time-consuming. Intuitively, this cost should be expected to increase as a group becomes larger, which could then select for a transition to hierarchy to keep the cost of playing the political game down as group size increases. However, previous work has lacked a mechanistic yet general model of political games that could formalize this argument and test the conditions under which it holds. We address this by formalizing the political game using a standard consensus formation model. We show that the increasing cost of forming a consensus over institutional rules selects for a transition from egalitarian to hierarchical organization over a wide range of conditions. Playing a political game to form institutional rules in this way captures and unites a previously disparate set of voluntary theories for hierarchy formation, and can explain why the increasing group size in the Neolithic would lead to strong political inequality. This article is part of the theme issue 'Evolutionary ecology of inequality'.

Welfare and performance of finishing pigs on commercial farms: Associations with group size, floor space per pig and feed type

Based on data from a field survey of 85 Norwegian farms, we aimed to investigate associations of group size, floor space per pig and type of feed with selected welfare- and performance indicators in finishing pigs. On each farm, we registered the number of pigs per pen, floor space per pig (m2), and the type of feed used (dry feed: n = 42 farms; liquid feed: n = 43 farms), once for every farm between 10:00–12:00 h within the last three weeks before slaughter. Ten pigs per pen from eight pens per farm were randomly chosen for sampling of welfare indicators (bite marks on ears, body and tail, hernia, and movement disorders, and a human approach test). A subsample of 44 farms recorded their production data in the Norwegian Ingris database. These farm level data included daily weight gain, feed conversion ratio, and mean weight of the slaughtered pigs. The pen-level data were analysed using a using a mixed model, with group size and floor space per pig (m2) as fixed effects, type of feed (liquid vs. dry feed) as a categorical variable, and individual “farm” as a random effect. The farm-level data were analysed using a generalized model with Poisson distribution and the same fixed factors. The proportions of pigs with bite marks on ears (P < 0.001) and body (P < 0.001) and daily weight gain (P < 0.001) decreased with increasing group size whereas avoidance of a novel human increased (P < 0.001). The proportion of pigs with bite marks on the body (P = 0.019) decreased with increasing floor space per pig. Providing dry feed ad libitum in vertical feeders resulted in a greater proportion of pigs with bite marks on the ears (P = 0.010) and the body (P = 0.029) than providing liquid feed intermittently in long troughs, but daily weight gain was higher with dry feeding (P < 0.001). Overall, low proportions of pigs had hernias (1.1 ± 0.001%) and movement disorders (1.7 ± 0.2%). In conclusion, our findings indicate that except for an increased avoidance of a novel human in larger groups, the pigs had better welfare in larger groups in terms of lower proportion of bite marks. Finally, more floor space per pig and liquid feed in feed troughs were also associated with a lower proportion of bite marks. As our data were skewed towards smaller group sizes and densities were skewed towards the legislated minimum space allowance per pig, the implications are limited to the range of conditions presented in the study.

Identification of social groups and waiting pedestrians at railway platforms using trajectory data.

To investigate the impact of social groups on waiting behaviour of passengers at railway platforms a method to identify social groups through the monitoring of distances between pedestrians and the stability of those distances over time is introduced. The method allows the recognition of groups using trajectories only and thus opens up the possibility of studying crowds in public places without constrains caused by privacy protection issues. Trajectories from a railway platform in Switzerland were used to analyse the waiting behaviour of passengers in dependence of waiting time as well as the size of social groups. The analysis of the trajectories shows that the portion of passengers travelling in groups reaches up to 10% during the week and increases to 20% on the weekends. 60% of the groups were pairs, larger groups were less frequent. With increasing group size, the mean speed of the members decreases. Individuals and pairs often choose waiting spots at the sides of the stairs and in vicinity of obstacles, while larger groups wait close to the platform entries. The results indicate that passengers choose waiting places according to the following criteria and ranking: shortest ways, direction of the next intended action, undisturbed places and ensured communication. While individual passengers often wait in places where they are undisturbed and do not hinder others, the dominating comfort criterion for groups is to ensure communication. The results regarding space requirements of waiting passengers could be used for different applications. E.g. to enhance the level of service concept assessing the comfort of different types of users, to avoid temporary bottlenecks to improve the boarding and alighting process or to increase the robustness of the performance of railway platforms during peak loads by optimising the pedestrian distribution.

Spatial patterns of large African cats: a large‐scale study on density, home range size, and home range overlap of lions Panthera leo and leopards Panthera pardus

Abstract Spatial patterns of and competition for resources by territorial carnivores are typically explained by two hypotheses: 1) the territorial defence hypothesis and 2) the searching efficiency hypothesis. According to the territorial defence hypothesis, when food resources are abundant, carnivore densities will be high and home ranges small. In addition, carnivores can maximise their necessary energy intake with minimal territorial defence. At medium resource levels, larger ranges will be needed, and it will become more economically beneficial to defend resources against a lower density of competitors. At low resource levels, carnivore densities will be low and home ranges large, but resources will be too scarce to make it beneficial to defend such large territories. Thus, home range overlap will be minimal at intermediate carnivore densities. According to the searching efficiency hypothesis, there is a cost to knowing a home range. Larger areas are harder to learn and easier to forget, so carnivores constantly need to keep their cognitive map updated by regularly revisiting parts of their home ranges. Consequently, when resources are scarce, carnivores require larger home ranges to acquire sufficient food. These larger home ranges lead to more overlap among individuals' ranges, so that overlap in home ranges is largest when food availability is the lowest. Since conspecific density is low when food availability is low, this hypothesis predicts that overlap is largest when densities are the lowest. We measured home range overlap and used a novel method to compare intraspecific home range overlaps for lions Panthera leo (n = 149) and leopards Panthera pardus (n = 111) in Africa. We estimated home range sizes from telemetry location data and gathered carnivore density data from the literature. Our results did not support the territorial defence hypothesis for either species. Lion prides increased their home range overlap at conspecific lower densities whereas leopards did not. Lion pride changes in overlap were primarily due to increases in group size at lower densities. By contrast, the unique dispersal strategies of leopards led to reduced overlap at lower densities. However, when human‐caused mortality was higher, leopards increased their home range overlap. Although lions and leopards are territorial, their territorial behaviour was less important than the acquisition of food in determining their space use. Such information is crucial for the future conservation of these two iconic African carnivores.

Red deer Cervus elaphus blink more in larger groups.

Most animals need to spend time being vigilant for predators, at the expense of other activities such as foraging. Group-living animals can benefit from the shared vigilance effort of other group members, with individuals reducing personal vigilance effort as group size increases. Behaviors like active scanning or head lifting are usually used to quantify vigilance but may not be accurate measures of this. We suggest that measuring an animal's blinking rate gives a meaningful measure of vigilance: increased blinking implies reduced vigilance, as the animal cannot detect predators when its eyes are closed. We describe an observational study of a captive population of red deer, where we measured the blinking rates of individual deer from groups of differing sizes (where mean group size ranged between 1 and 42.7 individuals). We demonstrate that as group size increases in red deer, individuals increase their blink rate, confirming the prediction that vigilance should decrease. Blinking is a simple non-invasive measure and offers a useful metric for assessing the welfare of animals experiencing an increase in perceived predation risk or other stressors.

Cooperation in Networked Collective-Action Groups: Information Access and Norm Enforcement in Groups of Different Sizes

Norms, typically enforced via sanctions, are key to resolving collective-action problems. But it is often impossible to know what each individual member is contributing to group efforts and enforce cooperation accordingly. Especially as group size increases, people commonly have access to the behaviors of—and can sanction—only those to whom they are tied in a broader network. Here we integrate two streams of research: one conceptualizing ties in networked collective-action groups as access to information about what others are doing and a second where ties represent information plus opportunities to enforce cooperation via punishment. While both have pointed to the cooperation benefits of more ties in the network, we argue that these benefits will depend on group size and whether ties provide access to information about what others are doing or whether they also entail opportunities for norm enforcement. Our experiment demonstrates that densely tied information networks facilitate cooperation but only when the group size is small. When people can also enforce their ties’ cooperation, however, densely tied networks particularly benefit larger groups. The results demonstrate how network-level properties and individual-level tie patterns intersect to promote contributions in small and large collective-action groups.

An Evaluation of Cesarean Delivery Rates According to Robson Classification in the Black Sea Region of Turkey

To analyse cesarean deliveries (CD) using the Ten Group Classification System (TGCS) for reducing cesarean rates. Cross-sectional study. Ordu University Medical Faculty Training and Research Hospital, Ordu, Turkey, from 1st January 2008 to 31st December 2020. A total of 29,885 deliveries during the 13-year study period were analysed. Group sizes and annual, overall, absolute, and relative CD rates were calculated to analyse the effect of the Robson groups (RGs)/TGCS. The data were analysed using the two-way Chi-square test and two-proportion Z-test with Bonferroni correction. The overall CD rate was 59.22% (17,697). The principal contributors to the overall CD rate were RG5 (54.48%), RG1 (12.52%), and RG2 (10.06%). The relative CD rate in preterm pregnancies (RG10) increased approximately five-fold over the 13-year study period due to the increase in both group size and absolute CD rate (p<0.001). TGCS shows the cesarean delivery trends in terms of cesarean rates and identifies those groups requiring special precautions. The target groups (RG5, RG1, RG2 and RG10) need more in-depth research to reduce CD rates. Various approaches need to be implemented including individualised cesarean indication, encouragement of vaginal delivery after cesarean delivery, expectant management in nulliparous women, and spontaneous labor for preterms labor. Cesarean section, Elective cesarean section, Induction of labor, Vaginal birth after cesarean section, Robson classification, Preterm deliveries.

THE PRODUCTIVITY OF EGG-CROSS CHICKENS DEPENDS ON THEM NUMBERS IN CAGES OF 12-TIER BATTERIES

The group size of hens is one of the key stimuli that affects the welfare of the bird. This is especially important for hens, which evolutionarily live in much smaller groups in the natural environment than in the conditions of enterprises producing edible eggs. But the specific parameters of hеns group size for keeping them in cages of multi-tiered batteries of traditional structures, known as "conventional cages" or "battery cages" according to the international classification, are not regulated by either domestic or foreign standards. There are only restrictions on the minimum number of chickens in one cage of batteries of "improved" designs ("modified enriched cages", or "furnished cages"). It should be at least 7 birds. Therefore, the purpose of the work was to study the productivity and efficiency of the production of edible eggs by increasing group size of hеns in cages of 12-tier batteries of traditional structures from 9 to 93 birds at the standard stocking density (area provision). For this, in the conditions of a modern complex for the production of edible eggs, 4 groups of hens were formed, each of which was kept in a separate poultry house-similar in area (2915 m2), equipped with 12-tier "Big Dutchman" cage batteries, the size and area of which cages differed. The group size of hens on 1st group was 9 birds/cage, 2 groups – 17 birds/cage, 3 groups – 52 birds/cage, 4 groups – 93 birds/cage, density of keeping hens of all groups – 22.6-23.1 birds/m2 with regulatory requirements no more than 25 birds/m2. It was established that an increase the group size of hens in cages from 9 to 93 birds contributes to an increase in the level of preservation (by 5.7%), laying per initial laying hen (by 9.1%), the volume of egg production (by 71.4%), in including based on the calculation per 1 m2 of the poultry house area, the level of profitability of their production from 34.7% to 40.1% and the reduction of the cost price from 1.70 to 1.56 UAH/egg.

A fellow-following-principle based group model and its application to fish school analysis

Group models based on simple rules are viewed as a bridge to clarifying animal group movements. The more similar a model to real-world observations, the closer it is to the essence of such movements. Inspired by the fish school, this study suggests a principle called fellow-following for group movements. More specifically, a simple-rules-based model was proposed and extended into a set of concrete rules, and two- and three-dimensional group models were established. The model results are intuitively similar to the fish school, and when the group size increases, the milling phase of both the model and fish school tends from unstable to stable. Further, we proposed a novel order parameter and a similarity measurement framework for group structures. The proposed model indicates the intuition similarity, consistency of dynamic characteristics, and static structure similarity with fish schools, which suggests that the principle of fellow-following may reveal the essence of fish school movements. Our work suggests a different approach for the self-organized formation of a swarm robotic system based on local information.

Does more matter? Critical mass and legislative influence

Scholars are divided on whether increased group size helps or hurts political minorities. We test the concept of “critical mass” using a different kind of long-time minority: pre-realignment Republicans in the American South. In Arkansas, after a century of token status, the minority party doubled its numbers in the late 1990s, held steady through the 2000s, then surged to a super majority. This stair-stepped transformation opened a unique window to address a question thus far examined only cross-sectionally: is an outgroup’s influence enhanced by an increase in numbers or does success become less likely as the majority reacts to a growing threat? We find support for the latter. As the minority expands, the likelihood their bills will be adopted, relative to majority bills, decreases markedly. The widened deficit is not, however, the consequence of diminished Republican success, but rather of a Democratic surge.

Using Unoccupied Aerial Vehicles to estimate availability and group size error for aerial surveys of coastal dolphins

AbstractAerial surveys are frequently used to estimate the abundance of marine mammals, but their accuracy is dependent upon obtaining a measure of the availability of animals to visual detection. Existing methods for characterizing availability have limitations and do not necessarily reflect true availability. Here, we present a method of using small, vessel‐launched, multi‐rotor Unoccupied Aerial Vehicles (UAVs, or drones) to collect video of dolphins to characterize availability and investigate error surrounding group size estimates. We collected over 20 h of aerial video of dive‐surfacing behaviour across 32 encounters with Australian humpback dolphins Sousa sahulensis off north‐western Australia. Mean surfacing and dive periods were 7.85 sec (se = 0.26) and 39.27 sec (se = 1.31) respectively. Dolphin encounters were split into 56 focal follows of consistent group composition to which example approaches to estimating availability were applied. Non‐instantaneous availability estimates, assuming a 7 sec observation window, ranged between 0.22 and 0.88, with a mean availability of 0.46 (CV = 0.34). Availability tended to increase with increasing group size. We found a downward bias in group size estimation, with true group size typically one individual more than would have been estimated by a human observer during a standard aerial survey. The variability of availability estimates between focal follows highlights the importance of sampling across a variety of group sizes, compositions and environmental conditions. Through data re‐sampling exercises, we explored the influence of sample size on availability estimates and their precision, with results providing an indication of target sample sizes to minimize bias in future research. We show that UAVs can provide an effective and relatively inexpensive method of characterizing dolphin availability with several advantages over existing approaches. The example estimates obtained for humpback dolphins are within the range of values obtained for other shallow‐water, small cetaceans, and will directly inform a government‐run program of aerial surveys in the region.

Tissue Oxidative Ecology along an Aridity Gradient in a Mammalian Subterranean Species.

Climate change has caused aridification which can alter habitat vegetation, soil and precipitation profiles potentially affecting resident species. Vegetation and soil profiles are important for subterranean mole-rats as increasing aridity causes soils to become harder and geophytes less evenly distributed, and the inter-geophyte distance increases. Mole-rats obtain all water and dietary requirements from geophytes, and thus digging in harder soils may amplify stressors (hyperthermia, dehydration- or exercise-induced damage). This study assessed the oxidative status of the wild common mole-rat along an aridity gradient (arid, semi-arid and mesic). Kidney and liver oxidative markers, including total oxidant status (TOS), total antioxidant capacity (TAC), oxidative stress index (OSI), malondialdehyde (MDA) and superoxide dismutase (SOD) were measured. Liver oxidative status did not demonstrate any significance with the degree of the aridity gradient. Aridity affected the TAC and OSI of the kidney, with individuals in the most arid habitats possessing the highest TAC. The evolution of increased group size to promote survival in African mole-rats in arid habitats may have resulted in the additional benefit of reduced oxidative stress in the kidneys. The SOD activity of the kidneys was higher than that of the liver with lower oxidative damage, suggesting this species pre-emptively protects its kidneys as these are important for water balance and retention.

What is simple is actually quite complex: A critical note on terminology in the domain of language and communication.

On the surface, the fields of animal communication and human linguistics have arrived at conflicting theories and conclusions with respect to the effect of social complexity on communicative complexity. For example, an increase in group size is argued to have opposite consequences on human versus animal communication systems: although an increase in human community size leads to some types of language simplification, an increase in animal group size leads to an increase in signal complexity. But do human and animal communication systems really show such a fundamental discrepancy? Our key message is that the tension between these two adjacent fields is the result of (a) a focus on different levels of analysis (namely, signal variation or grammar-like rules) and (b) an inconsistent use of terminology (namely, the terms "simple" and "complex"). By disentangling and clarifying these terms with respect to different measures of communicative complexity, we show that although animal and human communication systems indeed show some contradictory effects with respect to signal variability, they actually display essentially the same patterns with respect to grammar-like structure. This is despite the fact that the definitions of complexity and simplicity are actually aligned for signal variability, but diverge for grammatical structure. We conclude by advocating for the use of more objective and descriptive terms instead of terms such as "complexity," which can be applied uniformly for human and animal communication systems-leading to comparable descriptions of findings across species and promoting a more productive dialogue between fields. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Use of aerial distance sampling to estimate abundance of tule elk across a gradient of canopy cover and comparison to a concurrent fecal DNA spatial capture-recapture survey

Historically, aerial surveys have been used widely to monitor abundance of large mammals in the western United States. In California, such surveys have typically served as minimum count indices rather than true abundance estimates. Here, we evaluated the utility of aerial multiple covariate distance sampling (MCDS) to estimate abundance of three populations of tule elk (Cervus canadensis nannodes) in northern California. We also compared estimates and costs with published results from a concurrent fecal DNA spatial capture-recapture (SCR) survey. During December 2018 and 2019, we flew line transects for distance sampling of tule elk in Colusa and Lake counties. We modeled detection functions and evaluated effects of group size, canopy cover, and survey year. We averaged the top models comprising ≥0.95 of Akaike Model Weight and estimated abundance of both total and discrete populations. Detection probability increased with increasing group size and decreasing canopy cover. We estimated a two-year average total population size of N̂ = 674 elk (90% CI = 501–907) in our survey area which was similar to N̂ = 653 elk (90% CI = 573–745) from SCR estimates. Overall precision was greater (CV = 0.08; range = 0.11–0.30 by population) for SCR than for MCDS (CV = 0.18; range = 0.22–0.43 by population). Although estimates differed somewhat between methods for the individual populations, the combined estimate across the study region compared favorably. Total cost of SCR and MCDS surveys was $98,326 and $147,324, respectively. While SCR efforts were more precise and less expensive overall, our MCDS approach reduced staff time by 64% (587 person-hours) and the number of survey days by 87% (64 days). Our results suggest MCDS methods can produce reliable abundance estimates across a gradient of canopy cover, particularly when observations can be pooled across populations to decrease variance. We recommend future research to assess use of hybrid models, such as mark-recapture distance sampling or hierarchical distance sampling, to improve precision and estimation of detection probability.