Review Conservation Biology of Caecilian Amphibians DAVID J. GOWER * AND MARK WILKINSON Department of Zoology, The Natural History Museum, London SW7 5BD, United Kingdom Abstract: Most of the available data on declining populations of amphibians pertain to frogs and, to a lesser extent, salamanders. In keeping with their generally less understood biology, the population trends and conservation status of caecilian amphibians (Gymnophiona) are also much less known. We reviewed reports of threats to and declines of populations of caecilians. Despite a lack of field-study details (e.g., localities, dates, and sampling methods) and quantitative data, there are several recent reports of threats to and declines and extinctions of caecilians. A range of causal explanations (habitat loss, pollution, chytridiomycosis, and scien- tific collecting) for these perceived declines have been proposed but little or no associated evidence has been given. Although caecilians are often considered rare and thought to require pristine habitat, published, quan- titative data demonstrate that at least some species can occur in high abundance in disturbed, synanthropic environments. Few estimates of caecilian population parameters have been made and very few field methods have been tested, so the assumed rarity of any taxa remains inadequately demonstrated. Distribution and taxonomic data are also inadequate. Because they are generally poorly known and often cryptic, caecilians can be overlooked in standard faunal surveys, meaning that lack of opportunistic collection over several years might not represent evidence of decline. The conservation status of most species must be considered data defi- cient. More precise assessments will require a substantial increase in all areas of caecilian research, especially those involving new fieldwork. Future reports of caecilian conservation biology need to be explicit and more quantitative. Key Words: Amphibia, ecology, Global Amphibian Assessment, Gymnophiona, population declines, taxonomy Conservaci´ on de Anfibios Cecilianos Resumen: La mayor´ ıa de los datos disponibles sobre poblaciones de anfibios en declinaci´ on se refieren a ranas y en menor grado, a salamandras. En el marco del poco conocimiento de su biolog´ ıa, las tendencias poblacionales y el estatus de conservaci´ on de anfibios cecilianos (Gymnophiona) son mucho menos conocidos. Revisamos los reportes de amenazas a y declinaciones de poblaciones de cecilianos. A pesar de la falta de detalles de los estudios de campo (e.g., localidades, fechas y m´ etodos de muestreo) y de datos cuantitativos, hay varios reportes recientes de amenazas a y declinaciones y extinciones de cecilianos. Se han propuesto varias explicaciones de las causas (p´ erdida de h´ abitat, contaminaci´ on, chitridiomicosis, colecta cient´ ıfica) de estas declinaciones, pero con poca o ninguna evidencia asociada. Aunque los cecilianos a menudo son considerados raros y que requieren h´ abitat pr´ ıstino, hay datos, cuantitativos, publicados que demuestran que por lo menos algunas especies pueden ocurrir en abundancia elevada en ambientes sinantr´ opicos perturbados. Se han hecho escasas estimaciones de par´ ametros poblacionales de cecilianos y se han probado muy pocos m´ etodos de campo, as´ ı que la rareza asumida de cualquier tax´ on permanece inadecuadamente demostrada. Los datos taxon´ omicos y de distribuci´ on tambi´ en son inadecuados. Siendo generalmente poco conocidos y a menudo cr´ ıpticos, los cecilianos pueden ser pasados por alto en muestreos est´ andar de fauna, as´ ı que la falta de recolectas oportunistas a lo largo de varios a˜ nos puede no representar evidencia de declinaci´ on. El estatus de conservaci´ on de la mayor´ ıa de especies debe ser considerado como deficiente en datos. Evaluaciones m´ as precisas requerir´ an de un incremento considerable en todos los campos de investigaci´ on sobre cecilianos, * email d.gower@nhm.ac.uk Paper submitted December 12, 2003; revised manuscript accepted July 15, 2004. 45 Conservation Biology, Pages 45–55 Volume 19, No. 1, February 2005