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How many scales do pangolins have? This knowledge could help inform levels of threat and conservation action

Much of the illegal trade in pangolins involves their scales. As large shipments of scales continue to be seized, some weighing upwards of 12 tonnes (e.g., recent seizures in Singapore), understanding the magnitude of this trade and its impact on pangolin populations is crucial to informing conservation interventions and management for pangolins, and appropriate policy. This is particularly the case concerning African pangolins, which in the last decade have been trafficked internationally in large volumes, almost exclusively involving their scales, to Asian markets. Accurately estimating number of pangolins involved in such trade is critical, but doing so poses a significant challenge.

When consignments of whole pangolins (i.e., live or dead) are intercepted, they can be counted individually and are easily quantified. Yet what happens when a seizure involves only scales? The current method being used is based on the dry weight of scales (i.e., the proportion of a pangolin’s body mass that comprises dry scales), which is extrapolated to estimate the number of pangolins in a given consignment. However, there are a number of limitations to this method, namely that the dry weights are not representative of the eight pangolin species, while accurate and validated conversion parameters do not exist for the Indian, Philippine or any of the African pangolin species.

In recognition of the absence of accurate estimates for each species, in a recent paper, colleagues Dan Challender, Diogo Veríssimo and I, explored how knowledge of scale frequency could be used to develop an alternative sampling method for estimating the number of pangolins found in illegal trade. In turn, this could ultimately help understand the impact that illegal trade is having on populations by accurately quantifying offtake. To do so, we visited museums across the United Kingdom (and the American Museum of Natural History in New York) that held specimens of pangolins and counted the number of scales on 66 of them, representing all eight extant species from the genera Manis, Phataginus, and Smutsia.

Given the morphological diversity pangolins demonstrate in their scales, we were not surprised to find significant variation in the number of scales the eight species possess. The Philippine pangolin (Manis culionensis) was the ‘scaliest’, averaging 940 scales, while Temminck’s ground pangolin (Smutsia temminckii) was the least scaly, with an average of 382 scales. We also found variation within species groups, with substantial variation in the giant pangolin (509-664 scales) but less in the Chinese pangolin (527-581 scales).

Having calculated scale frequency, we developed a sampling method; a six-step process to extrapolate the number of pangolins represented in a seizure of scales based on scale frequency. While our method worked theoretically, we needed to understand the potential for application in a real-world context, and so we selected three likely scenarios in which it could be applied. These were:

  • Scenario A: extrapolation at the species level – where one or more species can be identified and the corresponding scale frequency means could be used
  • Scenario B: extrapolation at the continental level – where species identification is not possible, but the origin of the consignment is known (e.g., Africa)
  • Scenario C: where neither the species nor origin is known (as per the above example)

After critically assessing our method against the current weight-based one, we discussed the various limitations that still hinder it from being adopted. These are limitations mainly arising from the additional steps our method requires compared to the weight based method currently used; recognition of the additional time investment needed, the potential for sampling bias and miscalculation, and the noted lack of capacity among law enforcement personnel to identify which species specific pangolin scales belong to. These problems could potentially be overcome with the development of detailed guidance on sampling protocols, but it may be that our method is too complex to implement in a real world context, both for practical reasons but also because of accounting for biases between seizures would be difficult.

This was the first study to investigate scale frequency across the eight species of pangolin and the knowledge generated here, and through continued research, should assist in understanding pangolin trafficking dynamics.  The variation we observed in scale frequency also provides new insights into the morphological diversity of pangolins, adding to the growing body of work which explores this fascinating, but highly threatened group of mammals.

 

Tessa Ullmann

Volunteer researcher at the Sangha Pangolin Project, Durrell Institute of Conservation & Ecology, University of Kent, alumna, and member of the IUCN SSC Pangolin Specialist Group

 

The study was featured in this month’s special edition of Global Ecology and Conservation, ‘Pangolins: trade, ecology, and conservation’. Click here to read the full article.