Resumen del producto

¹ Instituto Politécnico Nacional, Centro Interdisciplinario de Ciencias Marinas

Steroid hormone assessment using non-invasive sample collection techniques can reveal the reproductivestatus of aquatic mammals and the physiological mechanisms by which they respond to changesin their environment. A portion of the eastern North Pacific blue whale (Balaenoptera musculus) populationthat seasonally visits the Gulf of California, Mexico has been monitored using photo-identifiedindividuals for over 30 years. The whales use the area in winter-early spring for nursing their calvesand feeding and it therefore is well suited for fecal sample collection. Using radioimmunoassays in 25fecal samples collected between 2009 and 2012 to determine reproductive state and stress, we validatedthree steroid hormones (progesterone, corticosterone and cortisol) in adult female blue whales. Femalesthat were categorized as pregnant had higher mean fecal progesterone metabolite concentrations(1292.6
415.6 ngg1) than resting and lactating females (14.0
3.7 ngg1; 23.0
5.4 ngg1, respectively).Females classified as pregnant also had higher concentrations of corticosterone metabolites(37.5
9.9 ngg1) than resting and lactating females (17.4
2.0 ngg1; 16.8
2.8 ngg1, respectively).In contrast, cortisol metabolite concentrations showed high variability between groups and no significantrelationship to reproductive state. We successfully determined preliminary baseline parameters of keysteroid hormones by reproductive state in adult female blue whales. The presence of pregnant or withluteal activity and known lactating females confirms that the Gulf of California is an important winterspringarea for the reproductive phase of these blue whales. The baseline corticosterone levels we aredeveloping will be useful for assessing the impact of the increasing coastal development and whalewatchingactivities on the whales in the Gulf of California

Palabras clave: Balaenoptera musculus; Pregnancy; Progesterone; Corticosterone; stress; Gulf of California

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