Ayo 2010 Ethology2 Chap.12 communication Introduction Communication Defined as the transfer of information from a signaler to a receiver Fig. 12.1 vervet ( 長尾黑顎猴 ) alarm calls Fig. 12.2 clever house Communication and honesty Communication solves problems How to coordinate group foraging How to find and secure a mate How to warn others about predators
Ayo 2010 Ethology3 Fig. 12.1 vervet alarm calls Vervets give different alarm calls depending on what type of predator has been sighted (A) here we see vervets standing up after hearing a “ chutter ” alarm call indicating that a snake has been spotted. When a leopard (B) is detected, vervets will give a “ barking ” alarm call and (C) climb up trees for safety.
7 Communication and honesty Selection is thought to favor the most economical way to share information. The natural selection should favor less exaggerated signals– which was referred to as “conspirational whispers”( 共謀低語 ). This is because signaling often involves some costs, and natural selection should favor minimizing these costs during conspirational whispers and hence reducing the conspicuousness( 惹人注目 )of the communication itself. For example, the case of ptarmigans ( 雷鳥 ). (Fig. 12.3) Both male and female rock ptarmigans are a stark white against the snow of winter.
Ayo 2010 Ethology8 the case of ptarmigans ( 雷鳥 ) Once spring arrive, females molt quickly, while males stay white, and as such the males are very conspicuous against the dark brown background (Fig. 12.3). Such conspicuousness attracts females, but it also attracts predators. As the breeding season progresses, rather than molting, males soil their plumage to become less conspicuous. Males communicate information to females via coloration, but when the period during which communication is useful comes to an end, they shut down the communication system in a cost-efficient manner – by soiling their white plumage.
10 Communication and honesty in toads Selection should favor females paying attention only to those cues that are in fact true indicators of larger size. The case in toads, in whom deep croaks can only be produced b large males because of the design of their vocal system. (Fig. 12.4) Female toads use the frequency of males ’ calls to gauge their potential mate ’ s size. Honesty is also possible when traits are not impossible, but merely very costly, to fake. (handicap principle).
Ayo 2010 Ethology12 Communication solves problems How to coordinate group foraging Food calls in birds Honeybees and the waggle dance Chemical and vibrational communication in foraging ants How to find and secure a mate Birdsong Aquatic insects How to warn others about predators Meerkats ( 狐獴 ) Alarm calls
Ayo 2010 Ethology13 Food calls in birds Colonial breeding cliff swallows live in nests that serve as “information centers”. Using both playback experiments and provision experiments (putting food out to entice birds), Brown and his team found that cliff swallows gave off “squeak( 吱吱叫 ) ” calls, which alerted conspecifics that a new food patch– often a swarm of insects– had been found (Table 12.1).
Ayo 2010 Ethology14 The mean number of birds and squeak calls heard two minutes before and two minutes after insects were flushed by foraging birds.
Ayo 2010 Ethology15 Under certain conditions, ravens emit a loud “yell” upon uncovering a new food source, such yells attract other birds.
Ayo 2010 Ethology16 Fig.12.6 yellers are hungry In ravens, “yelling” is often associated with foraging– in particular, calling others to a food bonanza.( 富礦帶 ) Immature ravens yell progressively more as a function of hunger. hungry birds call more often than satiated( 飽 足的 ) birds.
Ayo 2010 Ethology17 Captured birds to a location where there a new prey item that researchers had placed into the environment. Birds that had learned the location of prey acted as leaders. Fig. 12.7 Raven recruitment. The line denotes when the number of ravens that knew of the prey source equals the number of ravens at the prey source the next day. Green points indicate statistically significant recruitment Orange points indicate that recruitment was not statistically significant.
Ayo 2010 Ethology19 Honeybees and the waggle dance Fig. 12.8 bee foraging. Honeybee foraging involves a complex communication system, including waggle dances. This dance, along with other informational cues, gives bees in a hive information about the relative position of newly found food sources.
Ayo 2010 Ethology20 (A) Imagine a patch of flowers that is 1500 meters from a hive, at an angle 40 degrees to the right of the sun. (B) when a forager returns, the bee dances in a figure eight pattern. In this case, the angle between a bee’s “straight run” and vertical line is 40 degrees.
Ayo 2010 Ethology21 (C) The length of the straight run portion of the dance translates into distance from the hive to the food source.
Ayo 2010 Ethology22 Round danceSickle dance Waggle dance When resources are close to the hive, honeybee foragers tend to use round dance. When resource are at greater distances, sickle dance When food is very far from a hive, waggle dance
Ayo 2010 Ethology23 The number of “figure eight” circuits in a waggle dance when bees were raised at a temperature of 36 ℃ or 32 ℃ Bees from the 32 ℃ treatment were less likely to use the waggle dance when they returned to the hive than were bees from other treatments. Bees from 32 ℃ treatment made significantly fewer “circuits”. Bees raised in the 36 ℃ treatment fared much better in individual learning tasks.
Ayo 2010 Ethology24 Foraging ants (leaf-cutter ants) Leaves must first be cut, then carried to the nest, ground up, chewed and treated with enzymes, placed into a “fungus garden”, and subsequently cultivated. Two chemicals are particularly important, methyl 4-methylpyrrol-2-carboxylate and 3- ethyl-2,5 methylphrazine. These substance are produced in the poison gland and used to recruit fellow workers to foraging sites. Recruitment pheromones are incredibly powerful.
Ayo 2010 Ethology25 Leaf-cutter ants can ravage ( 毀滅 ) foliage in their path. The ants don’t attack all the leaves, however, but instead they often strip some leaves to the stalk, were leaving other leaves untouched.
Ayo 2010 Ethology26 Fig. 12.13 stridulating communication. A schematic of a leaf-cutter ant cutting a leaf and stridulating its gaster up and down. the vibrations were being sent along the length of a leaf in a long series of vibrational “chirps”. While only 40% of the ants stridulated when cutting tough leaves, the number increased to 70% when the leaves were tender, and to almost 100% when either type of leaf was dipped in sugar water.
Ayo 2010 Ethology28 Fig. 12.14 minim workers hitchhiking on a leaf These minim workers cannot cut leaves, but they are often found hitchhiking rides on leaves on the backs of leaf-cutters. Minim protect these other leaf-cutting ants from attack by parasitic flies. Hitchhiking minims apparently use the vibrational cues created by stridulating leaf- cutting nestmates to locate the leaf-cutters. The stridulating signals emitted by leaf-cutters are used in numerous contexts. One such venue is between leaf-cutters and minims, who use these signals to eventually hitch rides on cut leaves that are carried on leaf-cutters ’ backs.
Ayo 2010 Ethology30 How to find and secure a mate The role of (1) vocal communication (birdsong) (2) tactile communication (insects) Birdsong: In most species of songbirds, males don ’ t just learn a single song, they learn many different songs. For example, the song sparrow sings about ten different songs, the western marsh wren sings more than a hundred songs, and the brown thrasher sings an incredible thousand different songs.
Ayo 2010 Ethology31 Cowbirds The role of repertoire size in the mating success of male brown- headed cowbirds. Male cowbirds posses between two to eight different perched songs. Earlier studies indicated a correlation between the size of the perched song repertoire and mating success. Whether male repertoire size had an effect on female mate choice? Five different song treatments
Ayo 2010 Ethology32 Five different song treatments 1.Smaller repertoire: s single perched song sung three times in succession by a male Santa Barbara cowbird. 2.--- by a male Ventura cowbird. 3.Larger repertoire: three different perched songs sung in quick succession by a male Santa Barbara cowbird. 4.-- by a male Ventura cowbird. 5.A control: from a different species (song sparrow)
Ayo 2010 Ethology33 Copulation solicitation displays (CSDs) Youtube: http://www.youtube.com/watch?v=TQP91a-rhLw http://www.youtube.com/watch?v=TQP91a-rhLw The length of time that a female displayed ritualized “copulation solicitation displays” (CSDs) to different songs was recorded and used as a measure of female choice. Female cowbirds displayed longer CSDs when they heard cowbird versus song sparrow songs. Females show a marked increase in CSD times when exposed to males with large song repertoires (Fig.12.15) Female had longer CSDs when they were exposed to three different songs than to the same song played three times.
Ayo 2010 Ethology35 Phylogenetic studies of birdsong Sexual selection operates more strongly in polygynous mating systems and in systems that are sexually dimorphic (Fig. 12.16) Across 17 species of blackbirds, the maximum note length of songs increased as the size difference between males and females increased. There is strong competition for access to females, natural selection acts strongly on the many components that make up male song.
Ayo 2010 Ethology37 Birdsong from a proximate perspective Birdsong is incredibly diverse in terms of structure, pattern, tempo, frequency, and repertoire size. However, the vocal organ used in birds, the syrinx, varies little between different species. How is it possible that morphological invariance in the syrinx can translate into great diversity in birdsong? The syrinx has two compartments — left and right – and that the two sides of a bird ’ s brain can control these compartment independently.
Ayo 2010 Ethology38 Table 12.2 the different ways to sing Independent bilateral phonation: Operate both sides of the syrinx independently without one side being dominant. (Brown thrasher and gray catbirds) Unilateral dominance: Have one side of the syrinx dominate song generation. (Canaries) Alternating lateralization: Alternate which side of the syrinx dominates during a song. (Brown-headed cowbirds) Sequential lateralization: Have one side of the syrinx dominate for certain frequencies, and the other side dominate for the remainder of the frequencies used in a song. (Northern cardinal)
Ayo 2010 Ethology40 Ripple ( 波紋 ) communication and mate choice In water striders, ripples are usually produced by an up-and-down movement of the legs, with both right and left legs in synchrony and in constant contact with the water surface. The water striders produce different patterns of ripples for different kinds of behaviors, including signals for calling mates, courtship, copulation, post- copulation, sex discrimination, mate guarding, spacing, territoriality, and food defense.
Ayo 2010 Ethology42 Problem: how to warn others about predators Woodpecker and chickadee( 山雀 ) alarm calls Development, learning, and alarm call communication in meerkats Alarm calls as deceptive communication Male vervets ( 長尾黑顎猴 ) Dishonest alarm calls in swallows? (Fig. 12.20) Alarm calls in Richardson ’ s squirrels (Fig. 12.21) meerkats
Ayo 2010 Ethology43 While downy woodpeckers don’t give alarm calls when they are paired with same-sex partners, they emit such alarm calls when they are paired with a member of the opposite sex
Ayo 2010 Ethology44 Development, learning, and alarm call communication in meerkats Behavior observation indicates, compared to adults, Pups were initially more likely to respond to alarm calls in the presence of less dangerous or nondangerous predators, and they were more likely to ignore alarm calls emitted in the presence of dangerous predators. Pups don ’ t react as appropriately to alarm calls as adults. Fig. 12.19 age differences in reaction to alarm calls.
Ayo 2010 Ethology47 Alarm calls as deceptive communication Because alarm calls are a powerful form of communication– failure to listen might lead to death– natural selection should favor paying close attention to such calls. Nonetheless, these same selection pressures set up the possibility of using alarm calls in a deceptive manner. Using alarm calls in a deceptive manner is probably the exception rather than the rule.
Ayo 2010 Ethology48 Vervets ( 長尾黑顎猴 ) Verbets sometimes use deceptive predator alarm calls during some intergroup encounters – encounters that can lead to serious aggression between group members. Male verbets five an alarm call when encountering a new troop, even though no predator is in the vicinity. It was almost always a low- ranking male who gave the call.
Ayo 2010 Ethology49 Dishonest alarm calls in swallows? Male swallow may emit false alarm calls when they see their mate engaing in an extrapair copulation. These alarm calls break up extrapair matings. When females were absent during egg laying, the males who returned to their nests almost always gave false alarm calls. Male swallow who emitted false alarm calls during possible periods of extrapair copulations. (Fig. 12.20)
Ayo 2010 Ethology51 Alarm calls in Richardson’s squirrels When alarm calls become less reliable, natural selection should favor paying less and less attention to them. Two treatment (juveniles of squirrels) (Fig. 12.22) Heard a recorded alarm call and then saw a predator (true alarm calls) Heard a recorded alarm call. But no predator (false alarm calls)