Since the 1892 discovery of the Atlantic humpback dolphin Sousa teuszii (Delphinidae), a species endemic to coastal western Africa, from a skull collected in Cameroon, not a single record has been documented from the country or neighbouring countries. Increasing concern about the continued existence of the Gulf of Guinea population of S. teuszii or “Cameroon dolphin” prompted an exploratory survey in May 2011. Shore-based effort, on foot (30.52？km; 784？min), yielded no observations. Small boat-based surveys (259.1？km; 1008？min) resulted in a single documented sighting of ca. 10 (8–12) Cameroon dolphins in shallow water off an open sandy shore near Bouandjo in Cameroon's South Region. The combination of a low encounter rate of 3.86 individuals (100？km)？1 suggesting low abundance and evidence of both fisheries-caused mortality and of habitat encroachment raises concerns about the Cameroon dolphin's long-term conservation prospect. Our results add to indications concerning several other S. teuszii populations that the IUCN status designation of the species as “Vulnerable” may understate its threat level. 1. Introduction Here we describe coastal survey effort implemented in Cameroon in an attempt to relocate the “Cameroon dolphin,” that is, the Gulf of Guinea population of the Atlantic humpback dolphin Sousa teuszii (Kükenthal, 1892) [1]. This population has been “lost” to science since 1892 when German zoologist Willy Kükenthal described the new dolphin species Sotalia teuszii, later reassigned to the genus Sousa. The discovery was based on a single skull collected by the then head of plantations Mr. Eduard T？usz at Man O’War Bay, near Douala, in Cameroon’s Southeast Region. Although a second specimen was collected in 1925 in Senegal, it remained unrecognised till 1965 [2]. No other cases were documented for half a century and Cameroon remained the only known range state of S. teuszii, earning the species its vernacular name in several languages, for example, Cameroon (river) dolphin [3–6], Kamerun Delphin, Kamerun-Flussdelphin [6–8], and Dauphin du Cameroun [2, 6]. Finally, in 1943, a specimen was captured in a shark net off M’Bour, Senegal [9], while the first live individual was retrieved from a beach seine at Joal in 1956 [10]. Further S. teuszii records followed in western Africa, ranging from Dakhla Bay, Western Sahara, south to Angola [2, 11, 12]. As the species, after its discovery, was not reported again from Cameroon between 1892 and 2011, its historical link with the country faded and the species became known as the Atlantic humpback dolphin [6,
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