Herpetology: Chapter 9

What is the definition of communication?

What is the definition of communication?

“the cooperative transfer of information from a signaler to a receiver”

in order for communication to occur, need to produce a signal AND signal needs to be received.

What are the different modes of communication?

Visual communication: uses either body movement or distinctive shape or color

Acoustic communication: best known in anurans but some crocs and lizards and turtles can also call

Chemical communication: use odors derived from glandular secretions

Tactile communication: occurs when one individual rubs, presses, or hits part of body against another

Salamander communication

Salamanders have courtship glands.

Salander nose tapping to ID mates

Ambystoma talpoideum: circles around mate stimulating cloaca, male will then deposit sperm on the ground and external fertilization will occur (external fertilization requires constant contact)

How do frog calls and air flow balance?

Pump air into the lungs, they will close exits (the nose and mouth) and air pushes out into the vocal sac. This produces a sound.

Has to coordinate with ventilation to create a balance.

What is the primary mode of Frog communication?

acoustic signals primary communication in frogs.

What can influence frog calls?

Environmental and conspecific factors.

What is the significance of frog calls?

Females are looking for a specific call. Reproduction is largely dependent on male vocalizations for mate attraction, territory defense, and male-male interactions

How are frog calls variable/ manipulated?

Frog calls are capable of changing in males. (if it changes too much, speciation occurs)

Sometimes males synchronize calls and sometimes they alternate with each other. Synchronization makes them less obvious to predators. Alternating allows them to avoid competition with each other.

How are frog calls studied?

Many studies use playback techniques in artificial settings to learn how female frogs react to male calls. They have found that males show plasticity in response to other males (change).

Honest signal

way for a mate to tell just how fit you are. Detrimental to males.

Turtle communication

Visual and chemical signals.

Visual: different colors of carapace that can be used for species identification. Some emydid male turtles maneuver around female to expose color and striping pattern

Chemical: some turtles have Rathke’s glands on bridge of shell producing aromatic chemicals. Differentiation between male and female

Turtles can also fight. Male fighting occurs, but they will spend the night in burrow and continue the fight the next dy. Try to knock the other turtle on back to assert dominance. They can increase moment of rotation and velocity and use their head as an anchor point to swing themselves back up when knocked over.

Crocodilian communication

Use of auditory and visual signals

Grunting noise produced by bringing air in and moving down into the water then exhaling. This produces a vibration to create splashes in the water to produce visual signals while also creating a sound frequency in water.

Use of cloacal gland in mating

Tuatara communication

Rely on visual cues for male-male and male-female interactions For mating, male approaches female, mounts and moves leg to expose cloacal region to then internally fertilize.

Differentiation in lizard communication

each major clade emphasizes different sets of social signals

• iguania : visual

• gekkota : visual and auditory

• laterata : chemical

• scincimorpha : chemical

• anguimorpha : chemical

Amplexus

Used in frogs where they hold down the female in mating to prevent her from jumping out

Dewlap + head-bob

Dewlap coloration depends on species and will typically be flashed while doing a bob, a push-up with front limbs. Females prefer bright colors over drab colors

There is a pattern between push-ups and dewlap expansion that is also species specific

relationship between signal and performance complex. Vigor of pushup shows how strong males are as potential mates (most important component to attract female)

Signaling in lizards can also include extend legs, raise their tail or dorsoflatten

L. carinatus can curl their tail to look bigger, this ability is more important than push ups

Honest signaling in lizards

hard for a female to know how honest a signal is because push ups can be faked with just a head bob.

Snake communication

Chemical signaling for social communication, but tactile interactions are used between sexes.

Pheromones that attract males to females occur in skin on dorsal surface. Then tactile signals predominate in courtship once male has determined sex.

Snakes’ chemical sense

They have a forked tongue which can be used to determine which side of the body signals are coming from to direct their movement

Describe the process of snake mating communication + behavior

Phase 1: tactile chase

• weeds out weaker snakes, fitness

• approach and contact female then chase and mount

• Tactile acts include: undulation, dorsal body looping, caudocephalic waves, chin-rubbing, courtship biting, spurring, dorsal advance

Phase 2: Tactile alignment

• Tail search for copulatory event (looking for cloaca)

Phase 3: Intromission and coitus

• internal fertilization

• intromission (coital bite)

Snake attachment during courtship

Males will rub chin on females back and bite her. In snakes with vestigial limbs, pelvic spurs scratch the female in vicinity of her vent

Snake fighting

Male-male combat is common in viperids, colubrids, boids, and elapids. Not actually aiming to harm each other unless the submissive male will not give up.

(similar behavior in lizards)

How are mating systems categorized?

According to levels of polygamy within a species. This is a complex system of determining this level.

Operational sex ratio

receptive number of females to males, usually how many females : 100 males. This creates the basis for determining the level of polygamy

What are some factors that influence and behaviors associated with operational sex ratio?

Operational sex ratio is controlled by:

• Adult sex ratio

• density of population

• male mating capacity

• female mating capacity.

Operational sex ratio then influences intensity of intersexual competition as well as courtship frequency

Fecundity

Number of offspring (displayed on the y-axis)

What are the mating system categories?

Monogomy and polygamy are the two major mating systems

• Monogomy: fecundity is limited because mating occurs with only 1 individual. Once a mate is found there is no need to compete, sexual selection is not acting on system because it is not necessary there is no concern to improve selection if have mate. Typically includes high parental care

• Polygamy: sex selection is massive, how good mates are at finding signals, there is typically high competition

  • Polyandry: 1 female mates with many males. (or can be lots of females and 1 male with high competition between females)

  • Polygyny: limited females with many males (common system)

Describe the graphs of mating system categories success related to fecundity

Lines represent sexual selection gradient, what are they selected for (e.g coloration)

Steeper slope = sexual selection is acting upon system

Mating system of snakes

Most snakes are considered to have a polygamous mating system and a few are monogamous with high parental care.

Operational sex ratio in snakes depends largely on ecological factors and peculiarities of viviparous pit viper breeding biology.

Interpret the figure

This is an operation sex ratio graph that displays the complexity of its relationship between physiology and ecology, etc. If we see low reproduction cycles (amount of females available), may lead to low feeding success. Temperature could cause low reproductive cycles as well, lower feeding success, smaller body, meaning they are less capable of competing.

How does OSR relate to body size?

OSR when low can lead to sexual selection of body size which can lead to fighting where larger males win.

What is typically caused by a time when OSR was low?

Dimorphism