Increasing Intermammary Distance During Estrus in Bottlenose Dolphins (Tursiops truncatus)

Area of Science:

• Marine Biology
• Mammalian Reproduction
• Dolphin Endocrinology

Background:

• Mammary slits in cetaceans are key indicators of genital morphology changes.
• Intermammary distance increases in bottlenose dolphins before parturition.
• Estrus in mammals often involves external genitalia swelling.

Purpose of the Study:

• To investigate intermammary distance fluctuations in bottlenose dolphins during estrus.
• To identify concurrent morphological alterations associated with estrus.
• To assess the intermammary distance as a noninvasive estrus detection method.

Main Methods:

• Measured intermammary distance across seven ovulation cycles in three female bottlenose dolphins.
• Correlated intermammary distance with estrus status and serum estradiol levels.
• Analyzed the influence of body weight on intermammary distance.

Main Results:

• Intermammary distance was significantly greater on estrus days compared to nonestrus days (p < 0.05).
• A positive correlation was observed between intermammary distance and serum estradiol concentrations.
• Body weight also influenced intermammary distance, highlighting body shape changes.

Conclusions:

• Intermammary distance changes are strongly linked to estrus in bottlenose dolphins.
• This metric serves as an indicator of concurrent morphological modifications during estrus.
• Quantifying intermammary distance offers a promising noninvasive method for estrus detection in bottlenose dolphins.