Juan Capella

Migratory round-trip of individually identified humpback whales at the Strait of Magellan: clues on transit times and phylopatry to destinations

La ballena jorobada migra estacionalmente entre latitudes altas donde se alimenta en verano y latitudes bajas donde cria y se aparea en invierno. En el Pacifico sureste, la especie se reproduce en Colombia y Ecuador y se alimenta principalmente al oeste de la peninsula Antartica, y en el estrecho de Magallanes (EM) recientemente descrito como nueva area de alimentacion. Al comparar las fotografias de las colas de 62 ballenas individualizadas en el EM durante el verano austral entre 1999 y 2005 con 1.042 individuos de Colombia, se encontro a seis individuos comunes, lo que representa un indice de Intercambio migratorio de 0,093. Se registraron ocho migraciones para cuatro de estas ballenas entre el EM y Colombia en el ciclo migratorio de anos consecutivos. La distancia minima recorrida en una sola direccion vario entre 6.650 y 7.000 km. La duracion de los dos viajes mas rapidos registrados entre estos dos destinos fue de 88 y 99 dias, con una velocidad promedio de migracion de 76 y 67 km dia-1 respectivamente. Cinco de las seis ballenas comunes entre las areas fueron machos. Entre las seis ballenas se encontraron tres haplotipos de ADN mitocondrial todos descritos previamente en ballenas jorobadas de Colombia: tres ballenas con el haplotipo EM-1, dos con el EM-2 y uno con el EM-3. Los seis individuos se avistaron reiteradamente en el EM (hasta 39 dias en una estacion en un caso), con una permanencia promedio de 72 ± 40 dias (n = 20) por ano y un rango entre 3 y 125 dias. En promedio, estas seis ballenas se vieron durante el 71 ± 18 % de las siete temporadas muestreadas en el EM y tres se registraron seis de lo siete anos estudiados, por 4-6 anos consecutivos. Esta es la primera evidencia directa para incluir las ballenas jorobadas que se alimentan en el estrecho de Magallanes como parte de la poblacion del Pacifico sureste que se reproduce en aguas colombianas.

DIVERSIDAD Y DISTRIBUCIÓN ESTIVAL DE CETÁCEOS EN AGUAS INTERIORES DEL NORTE DE AISÉN, CHILE

Galletti, B., C. Carlson, E. Cabrera & R.L. Brownell Jr. 2006. Blue, sei and humpback whale sightings during 2006 field season in northwestern Isla de Chiloe, Chile. Paper SC/58/SH17 presented to the International Whaling Commission Scientific Committee, St. Kitts and Nevis, May 2006 (unpublished). 6pp.

Home sweet home: social dynamics and genetic variation of a long-term resident bottlenose dolphin population off the Chilean coast

Coastal resident and pelagic nonresident bottlenose dolphins, Tursiops truncatus , have been described in north-central Chile. Using long-term residence data (over 13 years of photo-identification) and genetic mtDNA information, we analysed the social dynamics through time and the genetic variation of this long-term resident population, and evaluated its sociogenetic interaction with nonresidents. Pelagic nonresident dolphins exhibited a higher level of genetic diversity than coastal residents and a significant difference in genetic structure was detected between them. Based on the difference in haplotype numbers and frequencies between resident and nonresident populations and between resident males and females, we propose a population dynamic model in which the resident population is composed of (1) resident females (founder lineages) and some of their female descendants that were born in and remained in the group, without effective female immigration from the nonresident population, (2) resident male descendants of the founder lineage that were born in and remained in the group and (3) resident males that were incorporated from the pelagic groups. Male-biased migration from nonresident pelagic groups into the resident population likely contributes to genetic variation and therefore may help limit inbreeding in the resident population. Finally, we propose that the peripatric model of population differentiation, where resident groups are sporadically connected to the pelagic population, may explain the origin of this unique resident population of bottlenose dolphins along the Chilean coast.