student presentations Flashcards
Honeyguides and Honey Gatherers
In parts of Africa, there are people who use honeyguides (birds) to find bees’ nests for honey. The Boran people of Kenya say that they can deduce the direction and distance to the nest based on the birds’ flight pattern, perching height, and calls.
The research has confirmed these claims
Red-billed Oxpeckers
Oxpeckers feed almost exclusively on what they can from the skin of large african mammals.The relationship is obligate for the birds, and it is generally assumed that hosts benefit through a reduction in tick load. I excluded oxpeckers from cattle as part of a controlled field experiment in Zimbabwe to test this idea. Changes in adult tick loads were unaffected by excluding the birds. In addition, oxpeckers significantly prolonged the healing time of wounds and removed earwax.
Results: parasitism rather than mutualism
Mafia Behavior from Parasitic Cowbirds
No nests were destroyed when cowbird access was always denied or when access was denied after we removed cowbird eggs, indicating that cowbirds were responsible. suggesting that cowbirds may occasionally ‘farm’’ hosts to create additional opportunities for parasitism.
Cowbirds parasitized most (85%) renests of the hosts whose nestswere depredated.
Kleptoparasitism by Fork-tailed Drongos
- kleptoparasitize food using both false alarms and physical attacks.
- Drongos made false alarms more frequently when kleptoparasitizing small food items, probably because these can be more profitably stolen by false alarm than attack.
- False alarms were also more frequent when targets were larger species, which are likely to be more costly to attack since they more frequently defended food.
- Drongos were able to attack targets when a false alarm had failed but rarely did so, even though such attacks were no less successful than attacks when no false alarm had been made.
It therefore appears that false alarms increase opportunities for kleptoparasitism because calls can be made when attacks are unprofitable. False alarm calls also appear to benefit drongos by increasing overall success in kleptoparasitism, because attacks could be made following failed false alarm calls.
Pre-dawn infertility by superb fairy-wrens
Bird that has the highest rate of extra-pair fertilization, and all females that were tracked had a pre-dawn foray with another male and subsequently had offspring sired by the male from the foray
results: the further they go the harder it is for a female to find another male
Deception and Cheaters with Rhesus Monkeys
Discoverers who failed to call, but were detected with food by other group members, received significantly more aggression than vocal discoverers.
Moreover, silent female discoverers ate significantly less food than vocal females.
This demonstrates that there are significant costs to withholding information. Such costs may constrain the frequency with which deception occurs in this and other populations.
Teaching in Wild Meerkats
we show that wild meerkats teach pups prey-handling skills by providing them with opportunities to interact with live prey. In response to changing pup
begging calls, helpers alter their prey-provisioning methods as pups grow older, thus accelerating
learning without the use of complex cognition.
The lack of evidence for teaching in species other than humans may reflect problems in producing unequivocal support for the occurrence of teaching, rather than the absence of teaching.
Fatherhood decreases testosterone in human males
In species in which males care for young, testosterone (T) is often high during mating periods but then declines to allow for caregiving of resulting offspring. Here, we use a large representative study in the Philippines to show that among single nonfathers at baseline men with high waking T were more likely to become partnered fathers by the time of follow-up 4.5 y later. Men who became partnered fathers then experienced large declines in waking and evening T, which were significantly greater than declines in single nonfathers.
Consistent with the hypothesis that child interaction suppresses T, fathers reporting 3 h or more of daily childcare had lower T at follow-up compared with fathers not involved in care. Our findings suggest that T mediates tradeoffs between mating and parenting in humans, as seen in other species in which fathers care for young.
Lizard threat display handicaps endurance
A restriction of aerobic metabolism can account for this effect. In threat posturing, lateral compression of the thorax may interfere with respiration or with circulation, limiting aerobic metabolism and causing a compensatory increase in anaerobic metabolism, thereby generating lactate and diminishing locomotor capacity.
Concentrations of lactate measured after display production were higher than baseline, consistent with the proposed mechanism. By restricting aerobic metabolism, the threat posture can act as a quality handicap, simultaneously advertising and expending the endurance capacity of displaying lizards.
Role of Footsize in Physical Attractiveness
Disparate cultural practices suggest that small foot size may contribute to female attractiveness. Two hypotheses potentially explain such a pattern. Sexual dimorphism in foot size may lead observers to view small feet as feminine and large feet as masculine. Alternately, because small female feet index both youth and nulliparity, evolution may have favored a male preference for this attribute in order
to maximize returns on male reproductive investment.
Using line drawings that varied only in regard to relative foot size, we examined judgments of attractiveness in nine cultures. Small foot size was generally preferred for females, while average foot size was preferred for males. These results provide preliminary support for the hypothesis that humans possess an evolved preference for small feet in females
Adaptions of Lions to Infanticide
Studies the effects that male takeovers have on lion prides and infanticide
Results:
Male takeovers result in high cub mortality
Females that remain in pride and mate with the new males have low fertility during first few takeovers
However, they show high sexual activity in the form of initiation of copulations and more mating partners
Show control over competition of males so that the largest coalitions become residents and can protect females for longer so that she can raise and produce more offspring
Bruce Effect in Wild Geladas
Female rodents are known to terminate pregnancies after exposure to unfamiliar males (“Bruce effect”).
Although laboratory support abounds, direct evidence for a Bruce effect under natural conditions is lacking. Here, we report a strong Bruce effect in a wild primate, the gelada.
Female geladas terminate 80% of pregnancies in the weeks after a dominant male is replaced. Further, data on interbirth intervals suggest that pregnancy termination offers fitness benefits for females whose offspring would otherwise be susceptible to infanticide.
Taken together, data support the hypothesis that the Bruce effect can be an adaptive strategy for females.
Why do Chimpanzees hunt and share meat?
observations were consistent with the male social bonding hypothesis. At Ngogo, male chimpanzees were likely to hunt when accompanied by other males. Males shared meat nonrandomly and reciprocally among themselves, and males exchanged meat for agonistic support.
Chimps hunt with tools
Tools were used in the manner of a spear, rather than a probe or rousing tool.
Females and immature chimpanzees exhibited this behavior more frequently than adult males.
Transient Masculinization in the Fossa
Through examination of wild and
captive fossas, androgen assays,
and DNA typing for confirmation of gender, we made the first
discovery of transient masculinization of a female mammal. Juvenile female fossas exhibited an enlarged, spinescent clitoris supported by an os clitoridis and a pigmented secretion on the underpart fur that in adults was confined to males. These features appeared to diminish with age. The majority of adult females lacked them, and os clitoridis length was inversely related to head-body length. No evidence was found to link this masculinization to elevated female androgen levels. Circulating concentrations of testosterone and androstenedione, but not dihydrotestosterone, were significantly lower in females than in
males.
No significant differences in testosterone, androstenedione, or dihydrotestosterone levels were found between juvenile (masculinized) and adult (nonmasculinized) females. There are several possible physiological mechanisms for this masculinization. None of the hypotheses so far proposed to explain the
evolutionary basis of female masculinization in mammals are
applicable to our findings.
Male Song Quality, Egg Size and Offspring Sex in Captive Canaries
sexy syllable song from male canaries resulted in a larger egg size because song was more taxing and therefore showed how fit male was. there was no result to show that it produced more male offspring
