herp 03/24/

  • X-Y Orientation

    • Definition: A type of navigation employed by amphibians and reptiles, particularly relating to their interaction with shorelines.

    • Importance of Shorelines:

      • Serve as a crucial interface between aquatic and terrestrial environments.

      • Act as landmarks for organisms navigating in these habitats.

  • Behavioral Examples of Orientation

    • Frogs:

      • Escape predators by jumping into water at approximately a 90-degree angle to the shoreline.

    • Tadpoles:

      • When threatened by aquatic predators, they move towards the shallow waters using the same 90-degree orientation from shorelines.

    • Metamorphs (post-tadpole frogs):

      • Similarly exit ponds following the same y-axis orientation during transformation.

  • Celestial Orientation

    • Mechanism: Amphibians utilize celestial cues (e.g., polarized light) for orientation.

    • Polarized Light:

      • Light scattered by molecules, particularly in the atmosphere, which can be detected by some amphibians and reptiles for navigation.

      • Fully polarized light occurs at 90 degrees to the plane of light entry.

    • Polarized Light Experiments:

      • Example: Study on Trachemys scripta (pond sliders) revealed their dependence on polarized light for navigation; they were disoriented under cloud cover which blocked polarized light.

  • Adaptations for Detecting Polarized Light

    • Specialized eye structures, particularly cones, allow some reptiles and amphibians to detect polarized light.

    • The relationship between reflection and polarization:

      • Water/Damp Soils:

        • Low reflectance but produce high amounts of polarized light, useful for organisms to identify water bodies.

      • Dry Soils:

        • High reflectance, low polarization, making them less useful as orientation cues.

  • Chemical Cues and Orientation

    • Amphibians also utilize chemical cues for orientation.

    • Anosmic creatures (surgically altered olfactory senses) show random orientation behaviors despite visual cues being available.

    • Example: Embiommia maculatum (spotted salamanders) orient towards paper towels soaked in water from their home ponds, demonstrating the use of chemical recognition for home location.

    • Snakes may also use chemical cues to find overwintering locations and reproductive opportunities via scent.

  • Magnetic Orientation

    • Species like Notophthalmus viridescens (eastern newt) possess magnetoreceptors to navigate via Earth's magnetic fields.

      • Conducted experiments revealing their ability to orient using varying light wavelengths (short wavelengths correlated to better orientation).

  • Homing Behavior in Sea Turtles

    • Sea turtles demonstrate remarkable navigational skills over long distances.

    • Hatchlings use the reflectance of celestial bodies to head toward oceans, then utilize wave action when they enter the water, moving perpendicular to the waves for navigation.

    • Maturity and returning to nest sites show high migratory accuracy, even over thousands of kilometers.

  • Light Pollution Issues

    • Artificial light disrupts the natural orientation of sea turtle hatchlings, resulting in misdirection toward urban areas instead of the ocean, leading to higher predation risks.

    • Solutions have included special low-intensity lighting to mitigate the impact of light pollution on wildlife while accommodating human needs.

  • Communication in Amphibians and Reptiles

    • Various modalities utilized: visual, chemical, acoustic, tactile.

    • Definitions and signs:

      • Communication involves a signaler and receiver, with signals being evolved behaviors for information transfer.

      • Cues provide information without evolutionary adaptation for the receiver.

  • Eavesdropping Behavior

    • Example: Tungara frogs call to attract females while unintentionally attracting predators (e.g., bats) due to the predator's ability to eavesdrop on these signals.

    • Dual selection pressure: Mating success versus predation risk complicates signal evolution and reception in amphibians.

  • Courtship Communication in Salamanders

    • Specifically observed in Bistemma talpoidium (mole salamander):

      • Unique courtship dances that involve physical interactions to stimulate mating behaviors.

      • Courtship must occur for successful reproductive outcomes, emphasizing the evolutionary adaptations in their reproductive behaviors.