Ecological and Taxonomic Notes on Calumma radamanus (Mertens, 1933) in the Antalaha Region of Northeastern Madagascar

Abstract 

Calumma radamanus is a small, soft-nosed chameleon endemic to the humid lowland forests of northeastern Madagascar. Long misclassified within the Calumma nasutum complex, it was revalidated through integrative taxonomic methods combining osteology, external morphology, and genetic data. This paper synthesizes morphological, ecological, and historical information with emphasis on populations in the Antalaha region. The species exemplifies cryptic biodiversity and highlights conservation needs in degraded Malagasy habitats. 

Keywords: Madagascar, chameleon, Calumma radamanus, Antalaha, taxonomy, conservation biology, cryptic species

Introduction 

Madagascar's reptilian fauna is highly endemic, with the genus Calumma representing an ecologically important group of arboreal chameleons. Calumma radamanus, originally described by Mertens (1933), was previously treated as a synonym of Calumma nasutum (Angel 1942), a classification that persisted for decades. Recent revisions using detailed osteological and genetic analysis by Prötzel et al. (2020) have revalidated C. radamanus as a distinct species, with a distribution restricted to northeastern Madagascar, including regions near Masoala National Park, Nosy Mangabe, Tampolo, and the Makira forest.

Etymology 

The name "radamanus" refers to the Col de Pierre Radama, the type locality of the species, which is named in honor of King Radama I of Madagascar (Mertens 1933). According to the International Code of Zoological Nomenclature Article 31.2.2, the name is treated as a noun in apposition and remains unaltered.

Morphological Diagnosis 

Specimens of C. radamanus exhibit a suite of distinctive traits. Adults measure 77–93.5 mm in total length, with snout-vent length ranging from 42.6 to 49.2 mm (Prötzel et al. 2020). The rostral appendage, present in both sexes, is short (1.4–1.7 mm), rounded, and oriented downward. The rostral scale is integrated into the appendage, differing from close relatives. Dorsal crest spines number between 6 and 8 in males. Males display greenish coloration with turquoise cheeks and nose, often marked by white lateral stripes and blue blotches. The casque is low in profile (0.8–1.5 mm), and internal cranial morphology reveals the absence of a parietal crest and frontoparietal fenestra. The squamosal bone remains widely separated from the parietal—a key diagnostic feature distinguishing the species from others in the nasutum complex (Prötzel et al. 2020).

Habitat and Distribution 

C. radamanus is found in low-elevation rainforests (7–500 m), particularly around the Antalaha region and Bay of Antongil. It prefers understory vegetation with thin-branched plants and is notably adaptable, appearing in secondary forest, edge habitats, and village gardens (Rabearivony et al. 2007). These habitats are increasingly impacted by slash-and-burn agriculture, vanilla plantation expansion, and illegal logging.

Behavior and Ecology 

The species is diurnal and arboreal, feeding on small arthropods using its ballistic tongue. At night, individuals shift to a pale beige coloration, presumably for camouflage (Madcham.de 2020). Although little is known about its reproduction, oviposition in soil is inferred, consistent with other Calumma species (Brady and Griffiths 1999).

Taxonomic History 

First described by Mertens (1933) based on specimens from the Bluntschli expedition, C. radamanuswas synonymized with C. nasutum (Angel 1942), resulting in decades of taxonomic confusion. Prötzel et al. (2020) resurrected the species using micro-CT imaging, external morphological comparison, and phylogenetic data, clarifying its status. The holotype and paratypes were deposited in European museum collections, although some specimens may be missing.

Conservation Status 

Despite lacking formal IUCN assessment, C. radamanus is presumed to be vulnerable due to ongoing deforestation and its limited distribution. Its survival in degraded habitats suggests a degree of ecological flexibility, but long-term conservation requires forest protection and habitat connectivity (Brady and Griffiths 1999; Prötzel et al. 2020).

Conclusion 

C. radamanus represents Madagascar's cryptic and localized biodiversity. Its rediscovery and revalidation underscore the importance of detailed taxonomic work for understanding and preserving the island's unique fauna. Focused conservation strategies and ecological monitoring are essential for the species' continued survival in northeastern Madagascar.

References

Angel, Fernand. 1942. Contribution à l'étude systématique des Chamaeleonidae de Madagascar. Mémoires du Muséum National d'Histoire Naturelle 6(2):183–261.

Brady, Lee D., and Richard A. Griffiths. 1999. Status Assessment of Chameleons in Madagascar. IUCN Species Survival Commission.

Madcham.de. . 2020. Calumma radamanus. Retrieved from https://www.madcham.de/en/calumma-radamanus/

Mertens, Robert. 1933. Die Reptilien der Madagaskar-Expedition Prof. Dr. H. Bluntschlis. Senckenbergiana Biologica15:260–274.

Prötzel, David, Mark D. Scherz, Fanomezana M. Ratsoavina, Miguel Vences, and Frank Glaw. 2020. Untangling the trees: Revision of the Calumma nasutum complex (Squamata: Chamaeleonidae). Vertebrate Zoology 70(1):23–59. https://doi.org/10.26049/VZ70-1-2020-3

Rabearivony, Jeanneney, Lee D. Brady, Richard K. B. Jenkins, and Odile R. Ravoahangimalala. 2007. Habitat use and abundance of a low-altitude chameleon assemblage in eastern Madagascar. Herpetological Journal 17(4):247–254.

ORIGINAL TEXT

Description of #Calumma_radamanus, with a special focus on its presence in the Antalaha region:---Calumma radamanus – The Soft-Nosed Chameleon of AntalahaOverviewCalumma radamanus is one of Madagascar's lesser-known but ecologically significant chameleon species. This small, soft-nosed chameleon is endemic to the humid lowland rainforests of northeastern Madagascar, including the coastal areas around Antalaha, where it can still be found in pockets of remaining forest.For decades, it was confused with other members of the Calumma nasutum group. But modern research using genetics and detailed morphology has confirmed that C. radamanus is a distinct species, worthy of its own conservation attention.---Physical DescriptionSize:Small and delicate, adult C. radamanus usually measures between 7.5 to 9.5 cm in total length, making it one of the smallest "true chameleons" in Madagascar.Nose:Both males and females have a short, soft, and downward-pointing rostral appendage, giving the species its nickname: the soft-nosed chameleon.Colouration:Males display vibrant green tones with striking turquoise lines or lateral stripes. Some individuals also show patches of blue or light yellow-green along the sides.Females tend to be duller, with a more uniform green or brownish-green colour, sometimes decorated with a faint lateral stripe or darker markings near the eyes.At Night:Like many chameleons, C. radamanus adopts a paler, beige-toned colouration at night, which helps with camouflage while sleeping.---Habitat in AntalahaThe lowland rainforests around Antalaha, particularly along the humid coastal strip near the Bay of Antongil and surrounding areas like Tampolo, are a natural refuge for C. radamanus. These forests are rich in biodiversity but increasingly threatened by:Slash-and-burn agricultureVanilla farming expansionIllegal loggingDespite these threats, C. radamanus still survives in secondary forests, along forest edges, and sometimes even in gardens close to the forest, making it one of the few small chameleons adapted to disturbed habitats in this part of Madagascar.---BehaviourLifestyle:Calumma radamanus is diurnal (active during the day) and mainly arboreal, usually found perched on small branches and shrubs at low to mid-height in the forest.Diet:It feeds primarily on small insects, such as flies, ants, and tiny beetles, which it captures with its projectile tongue.Reproduction:Like other chameleons, females lay eggs in the soil. However, little is known about the exact reproductive cycle of C. radamanus in the Antalaha region.---Conservation StatusAs of now, Calumma radamanus has no official IUCN Red List status, but given its limited distribution and the ongoing deforestation in the SAVA region, its populations are at potential risk.Threats Include:Habitat loss due to agricultureDeforestation for charcoal and timberClimate change impacts on coastal forestsProtecting the remaining forests near Antalaha is critical for the long-term survival of this species.---Why It Matters?Biodiversity Indicator:C. radamanus is a symbol of Madagascar's hidden biodiversity in Antalaha. Its survival reflects the health of the lowland rainforest ecosystems in northeastern Madagascar.Ecotourism Potential:For wildlife lovers visiting Antalaha, spotting C. radamanus offers a chance to encounter a rare and localized species not easily seen elsewhere.www.naturetourmadagascar.com---In SummaryThe soft-nosed chameleon of Antalaha (Calumma radamanus) is a small but fascinating reptile, living quietly in Madagascar's coastal rainforests. It represents both the beauty and fragility of Madagascar's endemic wildlife. Local conservation and responsible ecotourism could play a key role in ensuring this species continues to thrive in its natural habitat.