Seasonal trends and population status of the highly threatened Pteropus livingstonii in the Comoros archipelago.

Flying foxes of the genus Pteropus, especially those inhabiting islands, face increasing pressure from anthropogenic threats. A first step to implementing effective conservation actions is to establish monitoring projects to understand a species' population status and trend. Pteropus species are highly affected by seasonality which further requires regular, repeated, and long-term data to understand population trends, and reactions to severe weather events. In the present case study, a regular, bi-annual population census was implemented on Comoros between 2016 and 2023 for the highly threatened Livingstone's fruit bat, Pteropus livingstonii, and compared the results of standardized monitoring to historical population data. Seasonality had a large impact on the number of bats found at roost sites, with more bats present in the wet season, but the data over the past eight years revealed no significant in- or decrease in the number of bats counted on the island Anjouan. We estimated around 1,200-1,500 bats on Anjouan and 300-400 bats on Mohéli, and found that landcover type has no measurable effect on population distribution at roost sites. Our study highlights the need for long-term surveys to understand past population trends and that single counts are not sufficient to draw final conclusions of a species' status.

European Turtle Dove Population Trend in Greece Using Hunting Statistics of the Past 16-Year Period as Indices.

The European turtle dove is an important game bird for the hunters in Greece, which is one of a few European countries where its hunting is allowed. The sustainability of the species' hunting in Europe is discussed during the last several years due to declines in its population, which forced IUCN to classify it as vulnerable. In Greece, its harvest takes place from 20 August and lasts as long as the presence of the species in the country (mid-October). The ARTEMIS project is a Greek statistical database of hunting characteristics, as revealed by questionnaires distributed to hunters. Statistical indicators such as hunting opportunity and hunting harvest are considered in the literature as reliable to show the population trend of a game species. Therefore, in the present research, hunting statistics are used to determine the population trend of the European turtle dove in Greece. State-space modeling was the main procedure used, a method which allows us to deal with errors that exist from hunting bag data or hunting opportunity data assuming that on average the under and overestimations will be equal. The results of the modeling analysis show a stable trend of the variables used, i.e., hunting opportunity, hunting harvest, and juveniles to adult's ratio. Additionally, the hunting sustainability index showed that the sustainability of the species is improved annually, as a slight positive trend is revealed. This is in favor of the species, if it is considered that the actual percentage of the turtle dove population harvested is lower, since not all doves are encountered by hunters. It is concluded that for the period 2004/05-2019/20, as indicated by the hunting statistics, the population trend of the European turtle dove in Greece was stable and its harvest sustainable.

The present status, distribution, demography, and diet of the Dahl's Jird / Status atual, distribuição, demografia e dieta do Jird de Dahl

Meriones dahli (Shidlovsky, 1962) was previously accepted to be a subspecies of M. meridianus (Pallas, 1773). However, it was later suggested that they are geographically isolated from each other. Although hybridological studies and differences in certain external characteristics support the idea that M. dahli is a separate species, there are still doubts on its species status, and the exact range of its distribution is not known. In this paper, we provide some taxonomic information about the species, and compare these with the information given in previous studies. We argue that some differences exist among Armenian population regarding external measurements. Recent studies indicate that M. dahli is currently only distributed in Turkey, as an endemic mammal species. We provide predictions about the distribution of M. dahli, and report the estimated population size to its maximum value. Food preference studies for this species, conducted under laboratory conditions, are also introduced for the first time. We discuss the ecological data obtained from field studies, and emphasize that the habitat of M. dahli is about to disappear. Consequently, the protection status of this species should urgently be changed to the CR category and conservation studies must be carried out immediately.

Meriones dahli (Shidlovsky, 1962) foi previamente aceito como uma subespécie de M. meridianus (Pallas, 1773). No entanto, mais tarde, foi sugerido que eles estão geograficamente isolados um do outro. Embora estudos hibridológicos e diferenças em certas características externas apoiem a ideia de que M. dahli é uma espécie separada, ainda há dúvidas sobre o status de sua espécie, e a extensão exata de sua distribuição não é conhecida. Neste artigo, fornecemos algumas informações taxonômicas sobre as espécies e as comparamos com as informações fornecidas em estudos anteriores. Argumentamos que existem algumas diferenças entre a espécie armênia em relação às medidas externas. Estudos recentes indicam que M. dahli está atualmente distribuído apenas na Turquia como uma espécie endêmica de mamífero. Fornecemos previsões sobre a distribuição de M. dahli e relatamos o tamanho estimado da população em seu valor máximo. Estudos de preferência alimentar para essa espécie, conduzidos em condições de laboratório, também são introduzidos pela primeira vez. Discutimos sobre os dados ecológicos obtidos em estudos de campo e enfatizamos que o habitat de M. dahli está prestes a desaparecer. Consequentemente, o status de proteção dessa espécie deve ser alterado com urgência para a categoria CR, e estudos de conservação devem ser realizados imediatamente.

The present status, distribution, demography, and diet of the Dahl's Jird / Status atual, distribuição, demografia e dieta do Jird de Dahl

Meriones dahli (Shidlovsky, 1962) was previously accepted to be a subspecies of M. meridianus (Pallas, 1773). However, it was later suggested that they are geographically isolated from each other. Although hybridological studies and differences in certain external characteristics support the idea that M. dahli is a separate species, there are still doubts on its species status, and the exact range of its distribution is not known. In this paper, we provide some taxonomic information about the species, and compare these with the information given in previous studies. We argue that some differences exist among Armenian population regarding external measurements. Recent studies indicate that M. dahli is currently only distributed in Turkey, as an endemic mammal species. We provide predictions about the distribution of M. dahli, and report the estimated population size to its maximum value. Food preference studies for this species, conducted under laboratory conditions, are also introduced for the first time. We discuss the ecological data obtained from field studies, and emphasize that the habitat of M. dahli is about to disappear. Consequently, the protection status of this species should urgently be changed to the CR category and conservation studies must be carried out immediately.

Meriones dahli (Shidlovsky, 1962) foi previamente aceito como uma subespécie de M. meridianus (Pallas, 1773). No entanto, mais tarde, foi sugerido que eles estão geograficamente isolados um do outro. Embora estudos hibridológicos e diferenças em certas características externas apoiem a ideia de que M. dahli é uma espécie separada, ainda há dúvidas sobre o status de sua espécie, e a extensão exata de sua distribuição não é conhecida. Neste artigo, fornecemos algumas informações taxonômicas sobre as espécies e as comparamos com as informações fornecidas em estudos anteriores. Argumentamos que existem algumas diferenças entre a espécie armênia em relação às medidas externas. Estudos recentes indicam que M. dahli está atualmente distribuído apenas na Turquia como uma espécie endêmica de mamífero. Fornecemos previsões sobre a distribuição de M. dahli e relatamos o tamanho estimado da população em seu valor máximo. Estudos de preferência alimentar para essa espécie, conduzidos em condições de laboratório, também são introduzidos pela primeira vez. Discutimos sobre os dados ecológicos obtidos em estudos de campo e enfatizamos que o habitat de M. dahli está prestes a desaparecer. Consequentemente, o status de proteção dessa espécie deve ser alterado com urgência para a categoria CR, e estudos de conservação devem ser realizados imediatamente.

The present status, distribution, demography, and diet of the Dahls Jird

Abstract Meriones dahli (Shidlovsky, 1962) was previously accepted to be a subspecies of M. meridianus (Pallas, 1773). However, it was later suggested that they are geographically isolated from each other. Although hybridological studies and differences in certain external characteristics support the idea that M. dahli is a separate species, there are still doubts on its species status, and the exact range of its distribution is not known. In this paper, we provide some taxonomic information about the species, and compare these with the information given in previous studies. We argue that some differences exist among Armenian population regarding external measurements. Recent studies indicate that M. dahli is currently only distributed in Turkey, as an endemic mammal species. We provide predictions about the distribution of M. dahli, and report the estimated population size to its maximum value. Food preference studies for this species, conducted under laboratory conditions, are also introduced for the first time. We discuss the ecological data obtained from field studies, and emphasize that the habitat of M. dahli is about to disappear. Consequently, the protection status of this species should urgently be changed to the CR category and conservation studies must be carried out immediately.

Resumo Meriones dahli (Shidlovsky, 1962) foi previamente aceito como uma subespécie de M. meridianus (Pallas, 1773). No entanto, mais tarde, foi sugerido que eles estão geograficamente isolados um do outro. Embora estudos hibridológicos e diferenças em certas características externas apoiem a ideia de que M. dahli é uma espécie separada, ainda há dúvidas sobre o status de sua espécie, e a extensão exata de sua distribuição não é conhecida. Neste artigo, fornecemos algumas informações taxonômicas sobre as espécies e as comparamos com as informações fornecidas em estudos anteriores. Argumentamos que existem algumas diferenças entre a espécie armênia em relação às medidas externas. Estudos recentes indicam que M. dahli está atualmente distribuído apenas na Turquia como uma espécie endêmica de mamífero. Fornecemos previsões sobre a distribuição de M. dahli e relatamos o tamanho estimado da população em seu valor máximo. Estudos de preferência alimentar para essa espécie, conduzidos em condições de laboratório, também são introduzidos pela primeira vez. Discutimos sobre os dados ecológicos obtidos em estudos de campo e enfatizamos que o habitat de M. dahli está prestes a desaparecer. Consequentemente, o status de proteção dessa espécie deve ser alterado com urgência para a categoria CR, e estudos de conservação devem ser realizados imediatamente.

Land-Use Impact on Stand Structure and Fruit Yield of Tamarindus indica L. in the Drylands of Southeastern Ethiopia.

In this study, we evaluated stand status, dendrometric variables, and fruit production of Tamarind (Tamarindus indica L.) trees growing in bushland and farmland-use types in dryland areas of Ethiopia. The vegetation survey was conducted using the point-centered quarter method. The fruit yield of 54 trees was also evaluated. Tree density and fruit production in ha were estimated. There was a significant difference in Tamarind tree density between the two land-use types (p = 0.01). The mean fruit yield of farmland trees was significantly higher than that of bushland trees. However, Tamarind has unsustainable structure on farmlands. Differences in the dendrometric characteristics of trees were also observed between the two land-use types. Predictive models were selected for Tamarind fruit yield estimations in both land-use types. Although the majority of farmland trees produced <5000 fruit year-1, the selection of Tamarind germplasm in its natural ranges could improve production. Thus, the development of management plans to establish stands that have a more balanced diameter structure and thereby ensure continuity of the population and fruit yields is required in this area, particularly in the farmlands. This baseline information could assist elsewhere in areas that are facing similar challenges for the species due to land-use change.

Lack of recovery of the long-spined sea urchin Diadema antillarum Philippi in Puerto Rico 33 years after the Caribbean-wide mass mortality.

Caribbean populations of the long-spined black sea urchin Diadema antillarum Philippi were decimated by a disease-induced mass mortality in the early 1980's. The present study provides an updated status of the D. antillarum recovery and population characteristics in La Parguera Natural Reserve, Puerto Rico. The last detailed study to assess population recovery in 2001, indicated a slow, and modest recovery, albeit densities remained far below pre-mass mortality levels. Population densities were assessed along three depth intervals in six reef localities and one depth in three lagoonal sea-grass mounds using ten 20 m2 (10 × 2 m) belt-transects at each depth interval. Most of these were previously surveyed in 2001. All individuals encountered along the belt transects were sized in situ with calipers and rulers to characterize the size (age) structure of each population and get insight into the urchin's population dynamics and differences across localities in the area. Habitat complexity (rugosity) was assessed in all depth intervals. No significant differences in population densities between reef zones (inner shelf and mid-shelf) were observed, but significantly higher densities were found on shallow habitats (<5 m depth; 2.56 ± 1.6 ind/m2) compared to intermediate (7-12 m; 0.47 ± 0.8 ind/m2) and deep (>12 m; 0.04 ± 0.08 ind/m2) reef habitats in almost all sites surveyed. Habitat complexity had the greatest effect on population densities at all levels (site, zone and depth) with more rugose environments containing significantly higher densities and wider size structures. Comparison between survey years revealed that D. antillarum populations have not increased since 2001, and urchins seem to prefer shallower, more complex and productive areas of the reef. Populations were dominated by medium to large (5-9 cm in test diameter) individuals and size-frequency distributions indicated that smaller juveniles were virtually absent compared to 2001, which could reflect a recruitment-limited population and explain in part, the lack of increase in population densities. The limited temporal scale of this study, high horizontal movement of individuals along the complex, shallower reef and inshore habitats could also explain the general decline in mean densities. Other extrinsic factors affecting reproductive output and/or succesful recruitment and survival of juveniles likely contribute to the high variablility in population densities observed over time.

Trends in the detection of aquatic non-indigenous species across global marine, estuarine and freshwater ecosystems: A 50-year perspective.

Aim: The introduction of aquatic non-indigenous species (ANS) has become a major driver for global changes in species biogeography. We examined spatial patterns and temporal trends of ANS detections since 1965 to inform conservation policy and management. Location: Global. Methods: We assembled an extensive dataset of first records of detection of ANS (1965-2015) across 49 aquatic ecosystems, including the (a) year of first collection, (b) population status and (c) potential pathway(s) of introduction. Data were analysed at global and regional levels to assess patterns of detection rate, richness and transport pathways. Results: An annual mean of 43 (±16 SD) primary detections of ANS occurred-one new detection every 8.4 days for 50 years. The global rate of detections was relatively stable during 1965-1995, but increased rapidly after this time, peaking at roughly 66 primary detections per year during 2005-2010 and then declining marginally. Detection rates were variable within and across regions through time. Arthropods, molluscs and fishes were the most frequently reported ANS. Most ANS were likely introduced as stowaways in ships' ballast water or biofouling, although direct evidence is typically absent. Main conclusions: This synthesis highlights the magnitude of recent ANS detections, yet almost certainly represents an underestimate as many ANS go unreported due to limited search effort and diminishing taxonomic expertise. Temporal rates of detection are also confounded by reporting lags, likely contributing to the lower detection rate observed in recent years. There is a critical need to implement standardized, repeated methods across regions and taxa to improve the quality of global-scale comparisons and sustain core measures over longer time-scales. It will be fundamental to fill in knowledge gaps given that invasion data representing broad regions of the world's oceans are not yet readily available and to maintain knowledge pipelines for adaptive management.

Muskox status, recent variation, and uncertain future.

Muskoxen (Ovibos moschatus) are an integral component of Arctic biodiversity. Given low genetic diversity, their ability to respond to future and rapid Arctic change is unknown, although paleontological history demonstrates adaptability within limits. We discuss status and limitations of current monitoring, and summarize circumpolar status and recent variations, delineating all 55 endemic or translocated populations. Acknowledging uncertainties, global abundance is ca 170 000 muskoxen. Not all populations are thriving. Six populations are in decline, and as recently as the turn of the century, one of these was the largest population in the world, equaling ca 41% of today's total abundance. Climate, diseases, and anthropogenic changes are likely the principal drivers of muskox population change and result in multiple stressors that vary temporally and spatially. Impacts to muskoxen are precipitated by habitat loss/degradation, altered vegetation and species associations, pollution, and harvest. Which elements are relevant for a specific population will vary, as will their cumulative interactions. Our summaries highlight the importance of harmonizing existing data, intensifying long-term monitoring efforts including demographics and health assessments, standardizing and implementing monitoring protocols, and increasing stakeholder engagement/contributions.

Estado de la población del cocodrilo americano, Crocodylus acutus (Reptilia: Crocodilidae) y el caimán, Caiman crocodilus (Reptilia: Alligatoridae), en el Caribe central de Costa Rica

Dos especies de cocodrilianos han sido descritas en Costa Rica, el cocodrilo americano, Crocodylus acutus (Cuvier, 1807) y el caimán, Caiman crocodilus (Linnaeus, 1758). En Costa Rica se ha generado información de ambas especies, pero con énfasis en la vertiente del Pacífico, presumiblemente debido a su mayor desarrollo, lo cual ha acarreado mayor presión social hacia la atención de incidentes generados por el encuentro entre humanos y cocodrilos. El estudio se desarrolló durante el 2017 y en un área de aproximadamente 400 km2, caracterizada por tener una amplia densidad de cursos de agua que incluyen a los ríos: Matina, Pacuare, Reventazon y Parismina. En estos ríos se recorrió un promedio de 25 km desde la línea de costa hasta el interior del territorio, incluyendo los canales de Tortuguero, así como otros cuerpos de agua que conectan a estos ríos, lagunas importantes, y canales secundarios. Se realizaron tres repeticiones por segmento. Una población de 1 084 caimanes y 503 cocodrilos fue estimada, para una abundancia relativa de 8.64 y 2.80 ind/km respectivamente. Con respecto a caimanes poco más del 12 por ciento de los animales observados estaban en edad reproductiva, mientras que para cocodrilos sólo un 2 por ciento. La abundancia en los diferentes segmentos resultó ser significativamente diferente para ambas especies (Kruskal-Wallis, P 0.000). Mientras que la distribución por tallas de cocodrilos fue similar en todos los segmento (Kruskal-Wallis, P 0.15). Con 9 cocodrilos y 18 caimanes, reclutas o juveniles capturados, se calculó una proporción de sexos de 1.25 y 0.83 machos a hembras, para cocodrilos y caimanes respectivamente.

Two species of crocodilians have been described in Costa Rica, American crocodile, Crocodylus acutus (Cuvier, 1807), and caiman, Caiman crocodilus (Linnaeus 1758). In Costa Rica, data has been generated on both species, but populations in the Pacific have received more attention from researchers; presumably due to the fact that the Pacific slope has a greater development, which brings greater social pressure on the attention of the incidents generated by the encounter between humans and crocodiles. This study, performed during 2017, was done in an area of approximately 400 km2, characterized by having a wide and dense network of water courses, which includes the Matina, Pacuare, Reventazón and Parismina rivers. In these rivers, an average of 25 kilometers were traveled from the coastline up stream to the interior of the territory, including the Tortuguero canals, and other water bodies that connect these rivers, as well as in the most important lagoons and secondary channels. Three repetitions were made per segment. A population of 1 084 caimans and 503 crocodiles is estimated; for a sight count of 8.64 and 2.80 ind/Km respectively. Speaking of caimans, up to 12 por ciento of individuals of reproductive age were observed, while for crocodiles that number was only 2 por ciento. The abundance of both species in the different places studied, turned out to be significantly different for crocodiles and for caimans (Kruskal-Wallis, P 0.001). Likewise, the size distribution is similar for crocodiles reported in all environments (Kruskal-Wallis, p 0.15), while for caimans it indicates that there is a different distribution for sizes, according to the environment in which they are found (Kruskal -Wallis, P 0.001), with a bias against of the Pacuare and Matina rivers. It was possible to estimate a sex ratio of 1.25 and 0.83 males to females, in crocodiles and caimans respectively, with 9 and 11 captures in that same order, in recruit and juvenile sizes.

Predictive distribution modeling and population status of the endangered Macaca munzala in Arunachal Pradesh, India.

The present study reports the population of Macaca munzala in Tawang and West Kameng districts and its predictive distribution range in Arunachal Pradesh, estimated using ecological niche modeling. Environmental variables and occurrence data from a preliminary survey were used in the MaxEnt modeling, a statistical model to know the potential distribution area of the enigmatic species in Arunachal Pradesh. Later, a population survey was carried out in Tawang and West Kameng districts of the state following existing trails and paths. The distribution model revealed that only 2.4% of the total landmass of the state is potential distribution habitat range for M. munzala, whereas 10.19% of the total area of the two districts were shown to be potential habitat of the species. A total number of 971 individuals (including two solitary males) comprising 41 troops of M. munzala were recorded during the population survey. The mean troop size was 23.63 ± 1.21 individuals per troop ranging from 12 to 44 individuals. On average, M. munzala troops were comprised of juveniles (30.37%), adult females (23.83%), infants (18.22%), adult males (11.53%), sub-adult females (9.81%), and sub-adult males (6.23%). Our observed population size of M. munzala is higher in Tawang and West Kameng districts when compared with the earlier available records. This study showed the potential distribution of M. munzala based on environmental variables and the present population status in Tawang and West Kameng districts of Arunachal Pradesh, India.

Population Declines of Mountain Coqui (Eleutherodactylus portoricensis) in the Cordillera Central of Puerto Rico.

The Mountain Coqui (Eleutherodactylus portoricensis) is a frog endemic to montane rainforests in the Cordillera Central and Luquillo Mountains of Puerto Rico. Classified as endangered by the IUCN Red List and as vulnerable by the Department of Natural and Environmental Resources of Puerto Rico, this species has undergone considerable decline in the Luquillo Mountains. To evaluate the population status of E. portoricensis across its entire range, we conducted ~87 hours of surveys at 18 historical localities and 25 additional localities that we considered suitable for this species. We generated occupancy models to estimate the probability of occurrence at surveyed sites and to identify geographic and climatic factors affecting site occupancy. We also constructed a suitability map to visualize population status in relation to the presence of land cover at elevations where the species has been documented, and determined the dates when populations were last detected at historical localities. Eleutherodactylus portoricensis was detected at 14 of 43 localities, including 10 of 18 historical localities, but it was not detected at any localities west of Aibonito (western Cordillera Central). Occupancy models estimated the probability of occurrence for localities in the western Cordillera Central as zero. Site occupancy was positively associated with montane cloud forest, and negatively associated with the western Cordillera Central, maximum temperature, and precipitation seasonality. The suitability map suggests that declines have occurred despite the presence of suitable habitat. We suggest upgrading the extinction risk of E. portoricensis and potentially developing a captive breeding program for this species.

Mercury concentration in the eggs of four Canadian Arctic-breeding shorebirds not predicted based on their population statuses.

Methylmercury is a toxic form of mercury which persists in food webs for long periods of time and biomagnifies up successive trophic levels. Shorebirds breeding in the Arctic are exposed to methylmercury, derived from both natural and anthropogenic sources, when they ingest their invertebrate prey. Populations of many shorebird species are believed to be declining and one hypothesis for these declines is that they are due to detrimental effects of contaminants, including methylmercury. To test this hypothesis, we assessed mercury contamination in eggs of four Canadian Arctic-breeding shorebird species: black-bellied plover (Pluvialis squatarola), ruddy turnstone (Arenaria interpres), semipalmated plover (Charadrius semipalmatus) and white-rumped sandpiper (Calidris fuscicollis). Black-bellied plovers and ruddy turnstones are declining in the western hemisphere, whereas white-rumped sandpipers and semipalmated plovers have stable or slightly increasing populations. We found no relationship between egg mercury concentration and population trend for these four shorebird species. Intraspecific variation in mercury concentration was high. Notably, the mercury concentrations were much higher than levels found in a previous study of eggs of the same shorebird species from this same site, suggesting that mercury contamination may be subject to substantial inter-annual variation in the Canadian Arctic food web.

ESTATUS DE LA POBLACIÓN DE MONOS AULLADORES ROJOS EN EL CAÑÓN DEL BARBAS, FRAGMENTO MONTANO, CORDILLERA CENTRAL, Colombia / Status of the red howler monkeys population in the Barbas canion, montane fragment, central mountains, Colombia

Los bosques de montaña en Colombia han sufrido fuerte degradación por causas antrópicas y en la actualidad la mayoría son remanentes aislados e inmersos en hábitat antropogénicos. Los aulladores rojos han persistido en estas condiciones pero poco se conoce sobre su biología y respuesta a la alteración de su ambiente. Durante cinco meses en el 2005, evaluamos densidad y estatus poblacional de esta especie en la cuenca del río Barbas (Departamentos de Quindío y Risaralda), fragmento aislado de bosque montano bajo de 790 ha . Estimamos la densidad empleando censos por transectos lineales repetidos. Adicionalmente seguimos tropas de aulladores y evaluamos variables de vegetación teniendo en cuenta los requerimientos ecológicos de la especie. Estimamos una densidad de 11.7±6 grupos y 132.1±68 individuos/km2, superior a la usualmente reportada en bosques continuos. Esta alta densidad probablemente se deba al aislamiento del fragmento, que limita las posibilidades de dispersión de los aulladores. El tamaño promedio por tropa fue 11.3±2.5 individuos, con más de cinco machos y siete hembras adultas, y de uno a cuatro inmaduros. En general el bosque ofrece buena disponibilidad de recursos estructurales y alimenticios para los aulladores. Esta población no se encuentra amenazada en la actualidad por actividades antrópicas. El fragmento ha sido recientemente protegido bajo la figura de Parque Regional Natural y se adelantan corredores de conexión con otros remanentes cercanos. Sin embargo, esta población de aulladores se encuentra aislada de otras poblaciones y por tanto es urgente desarrollar medidas de manejo del paisaje para atenuar los efectos del aislamiento.

The montane forests in Colombia have suffered strong degradation due to human activities; currently, most of them are remnants isolated and immersed in anthropogenic habitats. The red howler monkeys have persisted in these conditions but little is known on their biology and response to the alteration of their environment. During five months in 2005, we evaluated the population density and status of this species in the basin of the Barbas River (Quindío and Risaralda departments), a low montane isolated forest fragment of 790 ha . We estimated density by censuses for linear repeated transects. Additionally we followed troops of howlers and evaluated vegetation variables according to howler ecological requirements. We estimated a density of 11.7±6 groups and 132.1±68 individuals per km2, higher than what is usually reported for this species in continuous forests. This high density might be caused due to the isolation of the fragment that reduces the possibilities of dispersion of the howlers. The average troop size was 11±2.5 individuals, with more than five males and seven females, and one to four immature individuals. In general, the forest offers to the howlers, good availability of food and structural resources. Currently, this population is not threatened by anthropogenic activities. Recently, this fragment has been protected as a Regional Park , and it exists a project to develop corridors of connection with others remnants. Nevertheless, this howler population is isolated of other populations, and therefore urgent measures of landscape management are needed to attenuate the effects of the isolation.