Revista Científica UDO Agrícola Universidad de Oriente Press ISSN: 1317-9152 Vol. 8, Num. 1, 2008, pp. 154-162

Revista Científica UDO Agrícola Vol. 8, Jan-Dec., No. 1, 2008, pp. 154-162

Notes on the confirmation of the Dwarf sperm whale Kogia sima Owen, 1866 (Cetacea: Kogiidae) on Venezuelan coasts 

Notas sobre la confirmación de la especie cachalote enano Kogia sima Owen, 1866 (Cetacea: Kogiidae) en las costas de Venezuela

Luis A. Bermúdez Villapol* ¹, Alejandro Sayegh ¹ And Tatiana León ²

¹Centro de Investigación de Cetáceos. E/S Los Robles, La Redoma de Los Robles, Isla de Margarita, estado Nueva Esparta, 6313, Venezuela, Telf: 58. 295.262.9752; Fax: 58. 295.262.3934 and ²La Universidad del Zulia, Facultad Experimental de Ciencias, Departamento de Biología. Maracaibo, estado Zulia. Venezuela. E-mails: cicvenezuela@yahoo.com, cicvzla@hotmail.com y tleonf@cantv.net  *Corresponding author 

Code Number: cg08020

ABSTRACT

The dwarf sperm whale, Kogia sima (Owen 1866), (Cetacea: Kogiidae) is distributed in tropical pelagic and temperate waters around the world, nevertheless, it is extremely hard to observe on field due to its habits of swimming deep waters, furthermore it can get easily confused with pygmy sperm whale species. K. breviceps (De Blainville 1828). Most data obtained from both species comes from stranded animals or incidentally caught ones. In the Caribbean and South America the information on these data is poor and scattered and little is known about the basic aspects of the species biology, life history, behaviour and distribution. K. sima had not been considered in the list of cetacean of Venezuelan waters until year 2001. To definitively establish the presence of the species K. sima in the country, four records are described here, based on the study of morphometric and/or craniometrical comparison of specimens or collected samples, a definite presence of dwarf sperm whale for territorial waters is proposed and therefore an extension in the distribution range for the southern Caribbean.

Key words: Pygmy sperm whale, Kogia sima Owen 1866, craniometry, morphometry, Venezuela.

RESUMEN

La especie cachalote enano Kogia sima (Owen, 1866) (Cetacea: Kogiidae), se distribuye en aguas pelágicas tropicales y templadas alrededor del mundo, sin embargo, es sumamente difícil de observar en campo debido a sus hábitos de aguas profundas, además  puede ser fácilmente confundible con la especie cachalote pigmeo, K. breviceps (De Blainville, 1828). La mayoría de la data obtenida de ambas especies proviene de animales varados, capturados incidentalmente o de restos de ellos. En Suramérica y el Caribe la información acerca de las mismas es muy pobre y dispersa, conociéndose muy poco acerca de aspectos básicos de su biología, historia de vida, comportamiento y distribución.  K. sima no había sido considerada en la lista de cetáceos de las aguas venezolanas hasta el año 2001. Con el objeto de ser establecida definitivamente la especie en el país, se describen cuatro registros, en base al estudio específico de comparación morfométrica y/o craneométrica de los ejemplares o muestras colectados, por lo que se propone la presencia definitiva del cachalote enano en aguas territoriales y por ende una ampliación del rango de distribución para el Caribe Sur.

Palabras clave: Cachalote enano, Kogia sima Owen 1866, craneometría, morfometría, Venezuela

INTRODUCTION 

The species of the Kogia genus, i.e. pygmy sperm whale Kogia breviceps (De Blainville, 1828) and dwarf sperm whale Kogia sima (Owens, 1866), have been reported for tropical pelagic and temperate waters around the world (Leatherwood et al., 1983; Hoyt, 1984; Caldwell and Caldwell, 1989, Waring et al., 2004). Initially both species were placed in the Family Physeteridae together with the sperm whale, Physeter macrocephalus, actually are recognized to as a distinctive family, Kogiidae (Rice, 1998). Nevertheless, biological works on both species are relatively few, besides that, the observation and differentiation of them, on field, are extremely difficult especially in rough waters (Jefferson et al., 1993; Bortolotto et al., 2003). Some studies of compared hematology and diet analysis speculate that Kogiids species are found almost exclusively in deep-water, but dwarf sperm whales appear to feed in shallower water than does K. breviceps. Both species are primarily teuthophagous (Baird, 2005; Bloodworth and Marshall, 2005; Santos et al., 2006). Thus, reports on the Kogia genus are mostly based on morphometry works from stranded animals. Zoogeography, physiology, life history and behavior of K. sima and K. breviceps in most regionsremain poorly understood (Muñoz-Hincapié et al., 1998; Marino et al., 2003; Chivers et al., 2005). On studies of the Order Cetacea for the Caribbean, both species are indicated as rare or uncommon, even though some records of specimens of the Kogia genus in countries with coasts on the Caribbean sea, as well as in South America are frequently reported (Felix et al., 1995; Muñoz-Hincapié et al., 1998; Debrot et al., 1998; Cardona-Maldonado and Mignucci-Giannoni 1999; Souza et al., 2003). For the Caribbean region, data on K. sima is only available for Saint Vincent and the Grenadines, Aruba, Klein Curacao, Puerto Rico and Bahamas (Cardona-Maldonado and Mignucci-Giannoni, 1999; MacLeod, 2004).

Kogiids have a distinctive dark dorsally and light ventrally color-pattern with a pronounced crescent shaped “false gill” like a shark’s gill slit on the side of its head (Jefferson et al., 1993). Nevertheless, external morphological characters can be confusing and produced incorrect species identifications, especially among younger animals (Chivers et al., 2005). In spite of a very similar morphology, K. sima, in an adult state, reaches maximum sizes of 2.7 m and have 8-13 pairs of teeth in the lower jaw, whereas K. breviceps exceeds the 3 m and has from 10-16 pairs of teeth in the lower jaw (Leatherwood et al., 1983; Caldwell and Caldwell, 1989). From the morphometric point of view, the best way to verify specimens of K. sima isto refer to the average obtained when comparing the percentages of the dorsal fin’s height against the total animal’s length; this value should be higher than 5% (Jefferson et al., 1993).  Also the average obtained when comparing the total body’s length with the distance from the tip of upper jaw to anterior edge of dorsal fin, which in the case of K. sima, being located in the middle point of the body, is lower than with K. breviceps (Ross, 1979; Debrot and Barros, 1992). Skulls of Kogia genus exhibit the greatest degree of asymmetry of all cetacean skulls (Ness, 1967). Compared craniometry of both species is also a valuable instrument for the identification or verification of species, especially if we compare the average between the rostrum length with the condylo-basal length; the range for K. sima is 28.5-41.5%, whereas for K. breciveps is 36.4-50.5% (Roos, 1979).

In Venezuela, the genus has not been considered very important because of the absence of reports and until now; there have been no records of the species K. breviceps (Bermúdez-Villapol and Boher, 2003).Nevertheless, the first evidence of the presence of the K. sima in territorial waters is based on the identification of a cranium located on the Zulia State coast in 1998 in the west of the country (León and Barrios, 2001).

To definitively establish the presence of K. sima in Venezuela, four records of genus Kogia were studied and compared. All of them came from stranded specimens or osteological samples, three of them from the west of the country and one from the northwest that constitutes, at the same time, the first record of a live stranding of K. sima in Venezuela.

MATERIALS AND METHODS 

In this work, four records of the Kogia genus were examined in order to confirm or rule out K. sima and K. breviceps species: two of them coming from data obtained through craniometrical study; samples classified as Nº MBLUZ-M-0225 and CLZV-MC-003 and previously recorded as K. sima. Comparative radius obtained by relating value data of face length (FL) with condilo-basal length (CBL) or total skull’s length, based on methodology suggested by Ross (1979), was used as a key tool for identification and confirmation. The other two records were based on the comparative morphometry of stranded animals in the western and eastern zones of the country respectively (Figure 1). In order to identify species, the representative percentage for each of the measures relative to the total length of the animals was established, including: the dorsal fin height, the length from tip of the snout to the first insertion point of the dorsal fin (anterior base), and the length from the tip of the snout to the blowhole. In the first specimen, comparison was based on guidelines from Jefferson et al. (1993) and Ross (1979). In the second specimen, it was identified following the percentage comparison of morphometric radius of the species K. sima and K. breviceps, according to guidelines from Ross (1979), Debrot (1992) and Barros et al. (1998).

RESULTS AND DISCUSSION 

Specimens studied 

First and Second report for the K. sima (western region)

By the year 2001, the species Kogia sima (Family Kogiidae)was reported for the first time in Venezuela based on the study of a skull found in 1998 in the northwest coast of Zulia State, Páez Municipality, in western Venezuela (11º 50,717’ N; 71º 20,633’ W) (Figure 2). The specimen was identified, initially by the third author (LT), as an adult specimen of K. sima, this was supported by the skull morphology of the sample (Figure 3). Craniometry applied at first was performed following the proposed methodology by Perrin (1975) and Bolaños (1995) and Ross (1979) proposal was not considered (Table 1). The collected material was found deposited in the Mammals Section of the Biology Museum of La Universidad del Zulia (MBLUZ by initials in Spanish) under catalog Nº MBLUZ-M-0225 (León and Barrios, 2001).

A second case, not published, was reported by the third of the authors  (LT) with the finding of an incomplete skull also located in 1998, on the coasts of Falcon State in western Venezuela (11º 03,367’ N; 71º 06,193’ W). The skull was initially identified as belonging to a young specimen of Kogia sima based mainly on morphological features. This osteological material resides in the Collection of the Laboratory of Zoology of Vertebrates (Mammalia Class, Cetacea Order) of the Experimental Faculty of Sciences, Biology Department, of La Universidad del Zulia, under the catalog number CLZV-MC-003.

To confirm or rule out of the species K. sima for both samples, the comparative averages obtained when associating the percentages of the value data of the rostrum length (RL) with the condylo-basal length (CBL), based on the methodology employed by Ross (1979) were used as a key instrument for identification.

In samples MBLUZ-M-0225 and CLZV-MC-003, averages of 30.22 and 27.45% respectively, were obtained.  The first is associated with described for K. sima (28.5-41.5%) (Ross, 1979),but the second is below this range. The latter result can be explained by the fact that it is a younger and smaller animal than adult specimens (Ross, 1979). These values confirm the species K. sima for both skulls, justifying the affirmation that the face of K. sima is shorter and smaller than half of the cranium length (León and Barrios, 2001).

Third report (western region)

By 16 June 2000, eight kilometers from Bajo San Bernardo, near San Carlos Island, in Municipality Almirante Padilla of Zulia State, (11º 02,185’ N; 71º 41,061’ W), a young specimen of the Kogia genus was found stranded (Figue 4). The body was later transported to Parque Sur de Maracaibo Fundation, thanks to the collaboration of the Coastguard Service and fishermen of the area, under the guidance of officials from the Ministry of Environment and Natural Resources (MINAMB by initials in Spanish) Zulia Environmental State Region; National Fund for Agricultural Research (FONAIAP by initials in Spanish) of Zulia Region and vets from the Parque Sur de Maracaibo, in order to perform a necropsy of the individual and determine its morphometry (Table 2).

The specimen was first identified, by officials from previously mentioned institutions, as K. sima based on the morphologic features of the animal.  In this work, confirmation of the species on this specimen were based guidelines by Jefferson et al. (1993) and Ross (1979) using the difference in percentage radiuses obtained from the morphometric data submitted.

Results demonstrated that the percentage of dorsal fin’s height in comparison with the total body length of the specimen was 7.4%, exceeding the 5% established for K. sima (Jefferson et al., 1993).  Similarly, the percentage obtained by comparing the length from the tip of the upper jaw to the anterior edge of dorsal fin in relation with the total body length of the specimen was 47.76%, under the minimum expected for K. breviceps (Ross, 1984). Therefore, the authors conclude that it is effectively a young specimen of K. sima.

Fourth report (eastern region)

On 16 June 2001, a specimen stranded live on La Punta Beach was assisted by the CIC staff (10° 53,28’N; 64° 03,616’W), El Guamache sector, to the southeast of Margarita Island (Sayegh et al., 2001) (Figure 5). After external examination of the specimen by the first two authors (BL and SA), six round injuries were found consuming the epithelium and the connective fat tissue, scarcely showing the muscle mass, no injury was bleeding and they looked healed on a general profile, as a light semi-round injury, showing a slit of the epithelium and fibrous exposure of the fat tissue, possibly produced by the cookie cutter shark, Isistius spp., reported for the tropical Atlantic (Compagno, 1984). Attacks by Isistius spp. has been reported on cetacean species in the Caribbean and northeastern Atlantic (Debrot and Barros, 1994; Perez-Sayas et al., 2002; Alardo et al., 2007). It is also the first reported evidence of wounds inflicted by cookie cutter sharkson any cetacean stranding case documented in the country (Figure 6).

The cetacean exhibited a complex start of fatigue, dehydration and metabolic dysfunction. Theanimal died at 15:30.

This specimen had a black to lead gray coloration on the dorsal region and on the head, with a light decrease in the coloration to the lateral sides, which lightens up on the ventral region until becoming white. The dorsal fin was high and sickled-shaped, located at the beginning of the last third of the body. The presence of a false gill was clearly noticed on the posterior region of both eyes. The specimen had an extended “U” shaped mouth, with no teeth, but eight pairs of bulges on the jaws were noticed. The identification of the species was made by the two first authors (BL and SA), through a percentage comparison of morphometric values of the species K. sima and K. breviceps, following guidelines from Ross (1979), Debrot (1992) and Barros et al. (1998) (Table 2).

Likewise, representative percentages of each of the measures of the total length of the specimen were established, being these considered as key features for the identification of the species: a) dorsal fin’s height with regard to the total body length; b) the length from the tip of upper jaw to anterior edge of  dorsal fin was 51 cm and represents 48.1% of the total body length, fitting with the comparative percentage for K. sima but different from the percentage for K. breviceps of 51.7%, that is superior, due to its position in the last third of the body. Also, the dorsal fin’s height according to the total body length of the animal was 8.5 cm equivalent to 8.01% of the total length, exceeding the established length for K. sima of 6% and exceeding by far the established length for K. breviceps of 3,8% in previous works (Debrot, 1992; Barros et al., 1998).

 The measure for the distance between the tip of the upper jaw to blowhole was of 8.5 cm which represents 8.01% of the length, completely different than the minimum established for K. breviceps of 10% (Ross, 1984). Therefore, the stranded animal is considered an immature specimen of the K. sima species.

The presence of K. sima is therefore confirmed for Venezuela, and is added to the 24 species for the country (Bermúdez-Villapol and Boher, 2003). Nevertheless, the paucity of records suggests a designation for the species in Venezuelan waters as “Data Deficient”.

Three reports from the western side of the country were recorded in the Gulf of Venezuela’s axis in coastal areas in which the continental shelf is extensively flat, with a slope fall that abruptly exceeds 3,000 m. This records suggests that K. sima might be associated with frontal areas all along continental shelf, as well as over the slope, in those areas with a high biomass of epipelagic zooplankton which makes up the diet of kogiids’ potential prey, which is mainly constituted by cephalopods (Baumgartneret al., 2001; Wang et al., 2002; Bloodworth and Marshall, 2005).

These data contribute to what little is known about this species in the Caribbean. The four confirmed records presented for Venezuelan waters represent most data for the southern Caribbeansuggesting that K. sima may not be common in the area.  K. sima has not been reported in areas close to the Venezuelan coasts or southern Caribbean waters, with the exception of records for Curacao and Klein Curacao (Debrot and Barros, 1992; Debrot et al., 1998), even if its presence can be expected in areas of the Colombian Caribbean (Cuervo-Díaz et al., 1986), Trinidad, Suriname (Muñoz-Hincapié et al., 1998) or Grenada (Romero et al., 2002).

CONCLUSION 

Comparison methods for differentiation of both species of the Kogia genus employed in the analysis in this work based on the relation of craniometric and morphometric radiuses, offered a solid basis to confirm the dwarf sperm whale species (Kogia sima Owen, 1866) for the reports indicated and rule out the pygmy sperm whale (K. breviceps De Blainville, 1828. These four records for the dwarf sperm whale on the eastern and western side of Venezuela, confirm the presence of the species in the list of cetaceans for the country’s waters; and therefore suggest an extension in the distribution range of it for the southern Caribbean.

ACKNOWLEDGEMENTS

To the Mammals Section of the Biology Museum of La Universidad del Zulia (MBLUZ) and the Zoology Laboratory of Vertebrate (Mammalia Class, Cetacea Order) of the Experimental Faculty of Sciences, Biology Department, LUZ. To the officials of the Environmental Direction of Zulia State, Ministry of Environment and Natural Ressources (DEAMINAMB-Zulia).

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