Mesoamerican cloud forests support a rich and unique biodiversity but face severe threats from increasing habitat degradation and climate change. Here, we present an updated overview of the amphibians and reptiles of Cusuco National Park (CNP), an isolated cloud forest in the Sierra de Omoa, Northwest Honduras. Based on surveys conducted over a 17-year period, we report the presence of 105 confirmed species of amphibians (30) and reptiles (75) within the reserve. This includes numerous threatened and regionally endemic amphibian species, as well as several reptile species previously unrecorded within the park. Given that it harbours approximately 26% of all recorded Honduran herpetofauna, our study highlights CNP as the most diverse forest region in Honduras with respect to the reptile and amphibian diversity documented to date. Our findings reinforce the plea to actively protect CNP as a globally valuable biodiversity hotspot and a centre of herpetofaunal endemicity. Furthermore, in the face of rapid deforestation across Mesoamerica, our findings highlight the need for expanded biodiversity studies across extant forest regions in Honduras to refine species distribution ranges and facilitate timely and effective conservation measures.

Los bosques nublados de Mesoamérica soportan una diversidad rica y única, pero por otro lado sufre de severas amenazas debido a la degradación del hábitat y el cambio climático. En este manuscrito presentamos un listado general de los anfibios y reptiles del parque Nacional Cusuco (CNP), un bosque nublado en la sierra de Omoa, noroccidente de Honduras. Basados en muestreos durante un periodo de 17 años reportamos la presencia de al menos 105 especies de anfibios (30) y reptiles (75) en la reserva. Dicha herpetofauna incluye numerosas especies endémicas y amenazadas de anfibios, así como algunos reptiles no registrados previamente en el área. Esto alberga el 26% de toda la herpetofauna conocida para Honduras, nuestro estudio remarca que CNP es la región forestal en Honduras con mayor diversidad de anfibios y reptiles con respecto a la diversidad documentada hasta la fecha. Nuestros encuentros refuerzan el hecho que se debe proteger activamente el CNP como un centro de alto valor global de biodiversidad y como un núcleo de endemicidad de herpetofauna. Además, en vista de la acelerada deforestación a través de los ecosistemas remanentes en Mesoamérica, nuestros datos son un llamado a realizar estudios a través de las regiones forestales existentes en Honduras, para refinar los rangos de distribución de las especies que permitan tomar las medidas efectivas de conservación.

Biodiversity hotspot, Cloud Forest, herpetofauna, IUCN status, Mesoamerica, Nuclear Central America, population monitoring, species list

Positioned centrally in Mesoamerica, Honduras is characterised by an extensive interior highland area (the Chortis Block) that extends from western Guatemala to Nicaragua (Alvarado et al. 2007; Townsend 2014). Biodiversity in this region is shaped by a multitude of environmental gradients and includes a range of isolated mountains topped by evergreen cloud forests, which can be broadly defined as “tropical forests frequently covered in a cloud of mist” (Stadtmuller 1987). These high-elevation forests exhibit highly specific bioclimatic conditions, constituting rare and unique ecosystems. Owing to their geographic isolation, Mesoamerican cloud forests form an array of ‘sky islands’ that provide habitat to a diverse and highly endemic fauna and flora. The diversity of the region is threatened by the rapid habitat degradation occurring throughout Mesoamerica’s forests (Brooks et al. 2002; Jung et al. 2022), with high-elevation ecosystems disproportionately impacted (Bubb et al. 2004). Despite their biological importance and elevated threat status, most remaining cloud forest habitats in Mesoamerica remain scientifically under-explored, hampering insights into the distribution of biodiversity across extended geographic areas (the Wallacean shortfall; Lomolino 2004). A better understanding of species diversity, abundance, and distributions is imperative to the timely and effective implementation of conservation measures.

Cusuco National Park (CNP), in northwestern Honduras, is an isolated, biologically diverse, yet threatened cloud forest ecosystem. CNP supports a rich herpetofaunal (reptile and amphibian) community, including many threatened and nationally or regionally endemic species. The park harbours four micro-endemic amphibian and four micro-endemic reptile species that are only known to occur at this single locality (Fig. 1). The forest ecosystem of CNP first gained protection for its value in protecting the watershed of the nearby city of San Pedro Sula. It is situated within the Mesoamerican biodiversity hotspot (Myers et al. 2000) and is globally recognised by the Alliance for Zero Extinction (2018) for the critical habitat it provides to its endemic amphibian fauna. Likewise, CNP was included in a global list of the most irreplaceable protected areas on the basis of its amphibian, bird, and mammal diversity (Le Saout et al. 2013) and is considered a Key Biodiversity Area by the IUCN. This illustrates the vital role of extant cloud forest systems in providing ecosystem services to nearby human communities (Bubb et al. 2004; Bruijnzeel et al. 2010).

Figure 1. 

The four amphibian and four reptile micro-endemic species currently known only to occur in Cusuco National Park. A Bolitoglossa diaphora B Oedipina tomasi C Plectrohyla dasypus D Plectrohyla exquisita E Anolis amplisquamosus F Geophis nephodrymus G Omoadiphas aurula H Rhadinella pegosalyta (Photographs provided by: Tom Brown A, E, F, G, H; Jesse Erens B; Achyuthan Srikanthan C, D).

More than 400 species of reptiles and amphibians have been recorded in Honduras to date, of which around 27% are endemic to the country (Solís et al. 2014; McCranie 2015). The first overview of the herpetofauna of CNP was presented by Wilson and McCranie (2004), which provided a list of 30 identified species based on surveys conducted from the late 1970s to the early 2000s. These findings prompted the start of a long-term monitoring programme to assess the herpetological diversity of the national park. As a result, the number of recorded species grew over subsequent years, and an updated inventory was published by Townsend et al. (2006), which increased the number of species identified in CNP to 50. This updated inventory was comprised of five salamanders, 12 frogs, 12 lizards, and 21 snakes, which were detailed in a subsequent field guide (Townsend and Wilson 2008). Whereas in the more recent works of Solís et al. (2017) and Martin et al. (2021), we included tentative overviews of the park’s reptiles and amphibians, these were different in scope and comprised incomplete species accounts. Hence, we here provide detailed results of the herpetofaunal surveys carried out in CNP across the subsequent 17 years spanning the period 2007–2023 and confirm the presence of 105 species of amphibians and reptiles within the park’s boundaries. In addition to providing an overview of all recorded herpetofauna, we discuss the global conservation significance of the reserve in view of continuing environmental change.

Following recurring survey efforts in the period 2007–2023, a total of 105 amphibian and reptile species have been confirmed in CNP: 30 amphibians (Table 1) and 75 reptiles (Table 2). Fig. 3 provides an overview of the cumulative number of species recorded over consecutive field seasons.

Figure 3. 

Species accumulation curves and logarithmic approximation of the reptile and amphibian species recorded in Cusuco National Park in the study period 2007–2023, following the earlier works of Wilson and McCranie (2004) and Townsend et al. (2006).

Amphibians

Since the inventory of 2006 (Townsend et al. 2006), an additional 13 amphibian species were recorded within the 17-year study period, of which a provisional overview was provided in Solís et al. (2017). Among some of the most notable records, the secretive species Nototriton brodiei Campbell & Smith, 1998 and Ecnomiohyla salvaje (Wilson et al. 1985) were both found in the high-elevation habitats of the CNP core zone. N. brodiei is a cryptic salamander that is typically found in dense leaf litter layers and in moss mats of intact montane forests (Kolby et al. 2009). The canopy-dwelling frog species E. salvaje, which is endemic to the region, is a cryptic species that is likely facing significant threats. There were only seven total reported adult individuals in Honduras, five of whom were observed in the core zone of CNP from 2009–2018 (Solís et al. 2017; Thorp et al. 2021). The park represents a crucial stronghold for this little-known species, as forests in Quebrada Grande, Copán, have disappeared, making the forests of CNP its main refuge.

The other newly recorded amphibians were mostly observed within lower-elevation habitats, largely within the buffer zone of CNP. Additions to the park’s salamander diversity stemming from these lower areas include Bolitoglossa dofleini (Werner 1903) and Bolitoglossa nympha Campbell et al., 2010, which are both endemic to nuclear Central America. The more widely distributed Bolitoglossa mexicana Duméril et al., 1854 was the final salamander species to be registered for CNP, with the first observation in 2013. Like the latter two salamanders, it seems to thrive in the areas of cattle pastures and agricultural plantations around Santo Tomas. Important anuran records include the Critically Endangered Honduran endemic Craugastor coffeus (McCranie and Köhler 1999), observed around the field site of Santo Tomas (also see Kolby 2009). We furthermore highlight the presence of the endangered Craugastor laevissimus (Werner 1896) (Suppl. material 1: plate 3) within CNP, following evaluation of photographic and bioacoustic observations made around the field site of Santo Tomas. The toad species Incilius campbelli (Mendelson 1994), endemic to nuclear Central America, was the final anuran reported for CNP, with a single individual observed close to Santo Tomas in 2013. No additional amphibian species were recorded in CNP during the subsequent decade (Fig. 3).

In addition to the four amphibian species that are endemic to CNP, three species in the park (and putatively Craugastor aff. nefrens) are endemic to Honduras, and 17 are endemic to nuclear Central America (Table 1). Almost half of the recorded amphibian species are presently listed as either Critically Endangered (five) or Endangered (eight), and four species are listed as Vulnerable (IUCN 2022). The threatened status of the amphibian diversity in CNP is reflected by their respective Environmental Vulnerability Scores (EVS), with a total of 18 amphibian species present in the park being attributed a high EVS (14–20), while just five species show a medium EVS (10–13), and six relatively widespread species show a relatively low EVS (3–9). Threatened amphibian species were found to be distributed across both the core and buffer zones, with the core zone presenting the sole refuge for several highly endangered taxa (Fig. 4).

Figure 4. 

The IUCN status of amphibian and reptile species recorded in the core and/or buffer zone of Cusuco National Park in the period 2007–2023. The delimitation of the core and buffer zones is based on the management plan of the Corporación Hondureña de Desarrollo Forestal (see Fig. 1). IUCN status: Critically Endangered (CR), Endangered (EN), Vulnerable (VU), Near-Threatened (NT), Least Concern (LC), and Not Evaluated (NE).

More than 400 species of amphibians and reptiles are currently reported to occur in Honduras (Solís et al. 2014; McCranie 2015). Within the core and buffer zones of CNP, at least 105 species have been recorded thus far, amounting to around 26% of recorded Honduran herpetofaunal diversity. This highlights CNP as an exceptionally diverse national park in Honduras and as a hotspot of Mesoamerican herpetofaunal diversity and endemicity. Its location at the northern edge of the biogeographically isolated Sierra del Merendón partially explains the relatively high number of micro-endemics (four amphibians and four reptiles). These observations are echoed by inventories of other species communities in CNP, where, for instance, birds (Martin et al. 2016), bats (Medina-van Berkum et al. 2020), and non-volant mammals (Hoskins et al. 2018) were also found to exhibit remarkable species diversity across its extensive elevational range. However, it is important to note that the park has received an exceptional amount of research effort over more than 15 years, which is much more than other Honduran cloud forest regions. There are several other protected zones in Honduras that exceed CNP in both land area and habitat diversity and show a similar elevational range (CNP reaching 2,243 m/asl). For instance, Pico Bonito National Park covers an area of 565 km² and ranges up to an elevation of 2,480 m/asl. Across a limited number of surveys, already 82 species of amphibians and reptiles were recorded in Pico Bonito National Park (McCranie and Solís 2013). Another example is the protected yet highly imperilled area of Texiguat, where 39 species of amphibians and reptiles have thus far been observed across a similar elevational gradient (Townsend et al. 2010). Hence, biodiversity assessments are urgently warranted in other extant cloud forest ecosystems in order to refine species distribution patterns across Honduras and the wider Mesoamerican biodiversity hotspot.

Early herpetofaunal surveys in CNP were largely focused on the eastern sections of the present-day core zone (Wilson and McCranie 2004; Townsend et al. 2006). Since then, the monitoring focus has been expanded to cover both the west side of the mountain as well as lower elevations, including transects situated in the warmer and drier habitats in the designated buffer zone of CNP (see Fig. 2C). Many additions to our updated species list, and in particular many reptile species, are a result of extended monitoring efforts in these previously underexplored habitats. This is reflected by a surge in new species records in the period 2007–2008 following the start of research activities in these field sites (Fig. 3). During the course of the study period, the rate of reptile and amphibian species detections slowed down considerably (Fig. 3), and we expect the large majority of the amphibian diversity inhabiting CNP to now be recorded. However, additional reptile species continued to be observed in recent field seasons in the period 2015–2023. In addition to observations of relatively thermophilic species at lower elevations, we expect that novel records in the reserve’s core zone might still arise from lesser studied microhabitats such as the forest canopy and in the form of cryptic leaf-litter dwelling or (semi) fossorial species. Further molecular studies may further highlight additional taxonomic diversity among the various species groups, which is likely to increase the known species diversity within the park. Thus, although we included 105 species in our updated species list, this figure is likely a conservative estimate.

While the herpetofauna diversity in CNP is unquestionably high, several species have been sighted only once during the study period, and records of several others are sporadically dispersed across many years. This pattern is particularly evident in snake species, which compose around 43% of the known herpetofauna in CNP. The resulting variability highlights the challenge of accurately determining seasonal species occurrence because detection can be subject to various environmental constraints. Consequently, assessing the true abundance, loss, or replacement rate of species in CNP becomes a considerable conservation challenge.

Furthermore, there remain potential additional records for several other snake species in the long-term database, such as Oxyrhopus petolarius (Linnaeus 1758), Ninia pavimentata (Bocourt 1883), and Rhadinella anachoreta (Smith and Campbell 1994). However, for the present study, we were unable to confirm them with certainty due to a lack of sufficient evidence, such as being identified by an expert or unambiguous photographic evidence. Additionally, Xenodon rabdocephalus (Wied-Neuwied 1824) is likely present in CNP, as indicated by photographs of two specimens (one roadkill) taken near the core and buffer zone in 2023 (Brown TW, pers. obs.), albeit recorded outside the annual survey season.

As a more comprehensive picture of the amphibian and reptile diversity in CNP is starting to take shape, continued monitoring efforts are becoming essential to assess the response of its herpetofaunal community to the combined effects of ongoing environmental change. With the solidification of a long-term dataset, future analyses can start shifting their focus to changes in relative species abundance and species distributions within the reserve. This is especially prudent given the notion that cloud forests are highly vulnerable to climatic change, with shifting temperature and precipitation regimes causing upslope elevational shifts in vegetation patterns and animal distribution ranges (Foster 2001; Laurance et al. 2011). As many specialised cloud forest species inhabit narrow microclimatic niches and, thus, highly specific elevational ranges, these changes have the potential to cause near-term extinctions (the “escalator to extinction” e.g., Freeman et al. 2018) and a shift in community composition. Such patterns have already started to form in CNP’s bird community (Neate-Clegg et al. 2018). As ectothermic vertebrate communities include relatively more high-elevation specialists (Laurance et al. 2011), these effects might be even more pronounced among herpetofauna.

Habitat destruction has been accelerating at an alarming pace and threatens all wildlife and habitats in CNP. Being a relatively small reserve with a core zone of 7,690 ha, which is largely isolated from other high-elevation habitats, this region is highly sensitive to disturbances. Despite its protected status as a national park, CNP has no permanent forest guards, and a growing population around the mountain, together with a challenging economic situation over the past decade, increases pressure on the remaining ecosystem. Deforestation for coffee plantations and livestock led to 7% of the park’s forested area being lost between 2000 and 2017 (Hoskins 2019). This deforestation is increasingly encroaching within the reserve’s core zone, posing an immediate threat to this vulnerable cloud forest ecosystem and its endemic species. As such, the combined effects of habitat degradation and climate change are likely to strongly exacerbate biodiversity loss within a short timeframe (Ponce-Reyes et al. 2012). The reserve’s buffer zone accommodates limited settlement and licenced farming practices and has little primary habitat left. Nevertheless, our findings across transects in the buffer zone indicate that the existing mosaic of disturbed forest fragments and anthropogenic landscape features still supports a wide variety of reptiles and amphibians. Besides the paramount importance of safeguarding the remaining pristine cloud forest in the core zone, sustained efforts are therefore also needed to preserve extant forest patches in the buffer zone. The protection of cloud forests such as CNP thus becomes increasingly dependent on successful community-based conservation schemes that incorporate sustainable socio-economic benefits to nearby livelihoods (Hostettler 2002; Bubb et al. 2004). For instance, payment for ecosystem services (PES) programmes might aid in the participatory protection of cloud forests. Nevertheless, this only becomes possible once the environmental value of cloud forests is adequately recognised and exceeds the short-term gains of habitat conversion (Martínez et al. 2009).

The persistence of many amphibian species in CNP is particularly jeopardised. Of the 13 species in the reserve that are listed as Critically Endangered or Endangered by the IUCN Red List, 11 are stated to be in continued decline, and in the other two, the population trend is unknown. In addition to other environmental stressors, the amphibian diversity in CNP is imperilled by the spread of emerging infectious diseases, most notably the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) (Longcore et al. 1999). This pathogen causes the lethal disease chytridiomycosis, which has been linked to global amphibian population declines and extinctions and has had especially devastating effects on Neotropical amphibian communities (Scheele et al. 2019). Reports of declines of Critically Endangered amphibian species in CNP prompted an investigation in 2007, revealing widespread Bd presence in the park with a high prevalence of infection in Endangered and Critically Endangered species, such as the endemic Plectrohyla dasypus McCranie & Wilson, 1981 and P. exquisita McCranie & Wilson, 1998; Kolby et al. 2010). An array of Bd dispersal mechanisms were identified in CNP, including detection not only in stream water and bromeliad reservoirs but also potential aerial dispersion by rainwater, waterfall spray, and residues on leaves resulting from contact with amphibian skin (Kolby et al. 2015 a, b). Stream-associated amphibians in CNP were found to be five times more susceptible to Bd infection than bromeliad-dependent species (Blooi et al. 2017). Yet, even strictly canopy-dwelling species can be infected; for example, Bd was detected in 100% (n=4) of the sampled E. salvaje during 2017–2018 (Thorp et al. 2021). Further investigation and continued disease monitoring in CNP are therefore crucial to detecting long-term changes in host-pathogen dynamics. The recently established Honduras Amphibian Rescue and Conservation Centre (HARCC) is actively researching methods to protect vulnerable species within habitats where this pathogen is present. On the upside, Craugastor milesi, a species previously listed as Extinct and now listed as Critically Endangered, was rediscovered in CNP in 2008 after last being seen in the 1980s when it was still locally abundant (see Kolby and McCranie 2009), thus providing prospects for its persistence in the park. A second observation of C. milesi (Kolby, Brown, Solis, pers. obs.) was registered in 2013, but subsequent monitoring efforts have failed to detect the species again, and it is possible the species might have disappeared from CNP in recent years (Solís et al. 2017). Its continued presence in the park thus remains to be reaffirmed. If the species has indeed disappeared from CNP, this would constitute the first local extinction among all previously documented herpetofaunal diversity (Wilson and McCranie 2004; Townsend et al. 2006; the present study).

Less information is available on the conservation status of reptile species present in CNP, with several remaining to be evaluated by the IUCN. However, an extended conservation assessment by García-Padilla et al. (2020) recently highlighted 11 amphibian and 12 reptile species in CNP as being among the most threatened ‘priority level’ species in Mesoamerica based on their combined endemic distribution range and high EVS scores. Their present IUCN status is therefore not an indication of lower conservation status than the amphibians, but rather indicates the absence of data sufficient to designate a particular level of concern, and thus many species urgently warrant further research and conservation attention. Furthermore, it can be expected that amphibian declines have cascading effects on reptile diversity, with reptile declines following the decline and extirpation of their amphibian prey (Zipkin et al. 2020). All the CNP endemic reptiles have been assessed by the IUCN Red List, including Anolis amplisquamosus (McCranie et al. 1993), which is listed as Critically Endangered and the three endemic snake species Geophis nephodrymus Townsend & Wilson, 2006, Omoadiphas aurula Köhler et al., 2001, and Rhadinella pegosalyta (McCranie, 2006), which are presently considered Vulnerable.

Much of the herpetofaunal diversity in Mesoamerica likely remains undescribed, with high rates of species discoveries taking place in concert with high rates of habitat destruction (Johnson et al. 2015; García-Padilla et al. 2020). Besides the Wallacean shortfall, uncertainty about the actual species diversity existing in areas (the Linnean shortfall) is, therefore, another factor hindering conservation efforts in biodiversity hotspots (Whittaker et al. 2005). Additional field surveys are therefore not only necessary to fill crucial knowledge gaps in species occurrences but also to gather the molecular, morphological, and ecological data necessary to disentangle undescribed diversity. DNA barcoding studies based on a standardised set of loci could, in this way, provide an increasingly affordable and scalable means to facilitate species delimitation in understudied tropical assemblages (Vences et al. 2005; Menegon et al. 2017). In CNP, an assessment of the cryptic species diversity within Anolis is presently underway, and further studies are assessing the status of several candidate species. Moreover, by gathering comparative genetic data across time, it could be evaluated to what extent populations retain their genetic diversity and connectivity within and between increasingly fragmented and imperilled forest regions (Dixo et al. 2009). While the present paper is directed at providing a renewed overview of herpetofaunal species richness in CNP, such complementary studies in the park, the broader Sierra de Omoa, and other forest regions across Honduras would therefore strongly benefit our understanding of regional biodiversity patterns and dynamics.

CNP is an irreplaceable hotspot of Mesoamerican biodiversity, providing habitat to a remarkable 105 species of reptiles and amphibians, including a high number of local, national, and regional endemics. Ongoing threats to CNP, in particular its high deforestation rates, place strong conservation urgency on this unique ecosystem and its biodiversity. A detailed understanding of the importance of CNP’s herpetofaunal community has only been possible due to our long-running monitoring program. Increased surveys in other extant forest regions are thus necessary to provide essential baseline biodiversity data and inform the timely and targeted conservation efforts necessary to safeguard the future of Mesoamerica’s irreplaceable herpetofaunal diversity.

This work is dedicated to Don Macrín Ramírez, a guardian of CNP for more than half a century and a personal inspiration to many who had the honour of meeting him whilst visiting his extraordinary forest home. During the course of his life, he was fortunate to marvel at much of the forest’s biodiversity in person. We hope and aim for his legacy to be kept alive. We would also like to express our sincere gratitude to all staff members, research associates, students, and park guides who contributed to the collection of amphibian and reptile observations at CNP over the years. We also thank the Instituto Nacional de Conservación Forestal (ICF) for providing annual research permits for biodiversity monitoring in CNP, and Operation Wallacea and Expediciones y Servicios Ambientales Cusuco for providing logistical support for all survey work completed in the park. We are grateful to Achyuthan Srikanthan, Silviu Petrovan, Alexander Hoad, Harry-Pym Davis, Rony Zunega, and Thais Lopes for providing photographs.