Small, smaller, smallest ...

Small, smaller, smallest ...

About the smallest islet populations of Podarcis pityusensis and Podarcis lilfordi, with first record of two new very small islet populations




In this article we make some notes on the smallest islet populations of Podarcis pityusensis (BOSCÁ, 1883) and Podarcis lilfordi (GÜNTHER, 1874), with a first description of two populations on Escull de Figueretes (Ibiza) and Carbó Petit (Menorca).


The endemic lizard of the Pityusic islands, Podarcis pityusensis (BOSCÁ, 1883), occurs on Ibiza, Formentera and 44 adjacent islands (MARTÍNEZ-RICA & CIRER 1982, SALVADOR 1986b, VAN DEN BERG 2010). Besides the endemic populations, Podarcis pityusensis is also translocated to mainland Spain (3 populations) and Mallorca (4 populations). The endemic lizard of the Balearic islands, Podarcis lilfordi (GÜNTHER, 1874), occurs on Mallorca with one small translocated population on the formerly island of s'Illot d'es Frares (ZAWADZKI 2010) and 10 surrounding islands, on Cabrera and 16 nearby islands, and on 16 adjacent islands of Menorca (SALVADOR 1986a, PÉREZ-MELLADO & SALVADOR 1988, PÉREZ-MELLADO 1989, TRIAY 1998, PÉREZ-MELLADO et al. 2008). So, in total 87 endemic island populations are described, ranging from some quite big islands, such as Cabrera and Dragonera, to a lot of very small islets, with Illot de Binicodrell Petit (Menorca) beeing the smallest one so far.
In this article we will describe islets with a surface under 1000 m², with newly found populations on two very small islets: Escull de Figueretes (Ibiza) and Illot d'en Carbó Petit (Menorca).

The smallest islets

We made an approximation of the dimensions of the islets with a surface less then 1000 m², measuring the islets in Google Earth. The results are listed in table 1. Eight islets meet this condition, of which five were previously described with a lizard population.

  Table 1: Dimensions of 8 small islets, derived from Google Earth, in (square) meters.

Illot d'en Carbonet

Carbonet is one of the six islands in front of Port d'Addaia, on the northeastern coast of Menorca (see map 1). PÉREZ-MELLADO et al. (2002) were the first to mention this island in literature. In their article on the redescription of Podarcis lilfordi carbonerae on Illot d'en Carbó, Illot d'en Carbonet was supposed to be seperated from Illot d'en Carbó recently, due to the small and shallow channel (filled with rocks, see image 3) between the two islets. They did not make an assessment of the (possible) population on this islet, “but it must be extremely small, due to its sparse vegetation and even smaller surface area available to the lizards” (compared to Carbó).

During 2009 and 2010 we did two small surveys on Illot d'en Carbonet. The area with plant cover is significantly smaller then on Illot d'en Carbó. Also the diversity of plant species is less, but we still found Arthrocnemum macrostachyum (or Sarcocornia fruticosa which looks very similar), Crithmum maritimum, Limonium sp. and Dactylis glomerata.
To our experience these conditions could be enough to sustain a small lizard population, but on both visits we were not able to find any lizards, nor secondary evidence of their presence, like feaces. However we did find two seagull chicks, and some protesting parents, what might be a reason for the absence of lizards on this islet, although the weather conditions during our 2010 visit, strong cold wind, certainly did not favour the situation as well.

  Map 1: Islands in front of Port d'Addaia.

  Image 1: Illot d'en Carbó (middle left) and Illot d'en Carbonet (middle right).

  Image 2: Illot d'en Carbonet with seagull chick.

  Image 3: Illot d'en Carbonet as seen from Illot d'en Carbó.

Illot d'en Carbó

Carbó is another one of the six islands in front of Port d'Addaia, on the northeastern coast of Menorca (see map 1). The history of the lizard population on Carbó island has some peculiar aspects (VAN DEN BERG & ZAWADZKI in press). Nevertheless, since 1989 the population of Carbó is mentioned as Podarcis lilfordi addayae (EISENTRAUT, 1928) (PÉREZ-MELLADO 1989), and since 2002 the population is described as Podarcis lilfordi carbonerae PÉREZ-MELLADO & SALVADOR, 1988 (PÉREZ-MELLADO et al. 2002). In the latter article the authors state that the specimens from Carbó differ from specimens of the other Addaia islands, by the dorsal color pattern. “In the case of Carbó most specimens have a more or less intense brown color, with in a minority combined with some green tones, while on the Addaia's dorsal olive-green tones are the majority. Dorsolateral lines are just visible, except for some juveniles and females. The ventral region is uniform gray or gray tones mixed with salmon, both in males and females.”
PÉREZ-MELLADO et al. (2008) calculated the adult population size on 65 specimens.

During our visits (2008, 2009 and 2010) on Carbó island, our observations match the population estimate of approximately 65 adult specimens. We could not find any nesting activity of seagulls, which supports the observations made by PÉREZ-MELLADO et al. (2008).
The plant cover compared to Carbonet island is much richer. Besides the earlier mentioned species Arthrocnemum macrostachyum, Crithmum maritimum, Limonium sp. and Dactylis glomerata, we also found Allium ampeloprasum, Lotus cytisoides and Anthemis maritima.
The lizards however did not show the strict dorsal color pattern as stated by PÉREZ-MELLADO et al. (2002). We did find lots of specimens with green tones, but this difference could be due to seasonal variation also seen in other subspecies of Podarcis lilfordi. Overall, a little tendency to melanism is clearly visible, especially in the tail of some specimens. During the 2008 survey, we could even spot one complete melanistic specimen (see image 10), regrettably not retrieved in 2009 or 2010.

  Image 7: Illot d'en Carbó - Female Podarcis lilfordi carbonerae.

  Image 9: Illot d'en Carbó - Male Podarcis lilfordi carbonerae.

  Image 4: Illot d'en Carbó, as seen from the northern part of the islet.

  Image 5: Illot d'en Carbó, as seen from the middle part of the islet.

  Image 6: Illot d'en Carbó - Female Podarcis lilfordi carbonerae.

  Image 8: Illot d'en Carbó - Female Podarcis lilfordi carbonerae.

  Image 10: Illot d'en Carbó - Melanistic specimen of Podarcis lilfordi carbonerae.