The handicap principle is a hypothesis proposed by Amotz Zahavi to explain how evolution may lead to "honest" or reliable signalling between animals which have an obvious motivation to bluff or deceive each other. It suggests that costly signals must be reliable signals, costing the signaller something that could not be afforded by an individual with less of a particular trait. For example, in sexual selection, the theory suggests that animals of greater biological fitness signal this status through handicapping behaviour, or morphology that effectively lowers this quality. The central idea is that sexually selected traits function like conspicuous consumption, signalling the ability to afford to squander a resource. Receivers then know that the signal indicates quality, because inferior quality signallers are unable to produce such wastefully extravagant signals.
The Coolidge effect is a biological phenomenon seen in animals, whereby males exhibit renewed sexual interest whenever a new female is introduced to have sex with, even after cessation of sex with prior but still available sexual partners. To a lesser extent, the effect is also seen among females with regard to their mates.
The speckled wood is a butterfly found in and on the borders of woodland areas throughout much of the Palearctic realm. The species is subdivided into multiple subspecies, including Pararge aegeria aegeria, Pararge aegeria tircis, Pararge aegeria oblita, and Pararge aegeria insula. The color of this butterfly varies between subspecies. The existence of these subspecies is due to variation in morphology down a gradient corresponding to a geographic cline. The background of the wings ranges from brown to orange, and the spots are either pale yellow, white, cream, or a tawny orange. The speckled wood feeds on a variety of grass species. The males of this species exhibit two types of mate locating behaviors: territorial defense and patrolling. The proportion of males exhibiting these two strategies changes based on ecological conditions. The monandrous female must choose which type of male can help her reproduce successfully. Her decision is heavily influenced by environmental conditions.
Sperm competition is the competitive process between spermatozoa of two or more different males to fertilize the same egg during sexual reproduction. Competition can occur when females have multiple potential mating partners. Greater choice and variety of mates increases a female's chance to produce more viable offspring. However, multiple mates for a female means each individual male has decreased chances of producing offspring. Sperm competition is an evolutionary pressure on males, and has led to the development of adaptations to increase males' chance of reproductive success. Sperm competition results in a sexual conflict of interest between males and females. Males have evolved several defensive tactics including: mate-guarding, mating plugs, and releasing toxic seminal substances to reduce female re-mating tendencies to cope with sperm competition. Offensive tactics of sperm competition involve direct interference by one male on the reproductive success of another male, for instance by physically removing another male's sperm prior to mating with a female. For an example, see Gryllus bimaculatus.
A spermatophore or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especially salamanders and arthropods, and transferred in entirety to the female's ovipore during reproduction. Spermatophores may additionally contain nourishment for the female, in which case it is called a nuptial gift, as in the instance of bush crickets. In the case of the toxic moth Utetheisa ornatrix, the spermatophore includes sperm, nutrients, and pyrrolizidine alkaloids which prevent predation because it is poisonous to most organisms. However, in some species such as the Edith's checkerspot butterfly, the "gift" provides little nutrient value. The weight of the spermatophore transferred at mating has little effect on female reproductive output.
Anisogamy is the form of sexual reproduction that involves the union or fusion of two gametes, which differ in size and/or form. The smaller gamete is considered to be male, whereas the larger gamete is regarded as female.
Stalk-eyed flies are insects of the fly family Diopsidae. The family is distinguished from most other flies by the possession of "eyestalks": projections from the sides of the head with the eyes at the end. Some fly species from other families such as Drosophilidae, Platystomatidae, Richardiidae, and Tephritidae have similar heads, but the unique character of the Diopsidae is that their antennae are located on the stalk, rather than in the middle of the head as in all other flies.
Sexual conflict or sexual antagonism occurs when the two sexes have conflicting optimal fitness strategies concerning reproduction, particularly over the mode and frequency of mating, potentially leading to an evolutionary arms race between males and females. In one example, males may benefit from multiple matings, while multiple matings may harm or endanger females, due to the anatomical differences of that species.
A courtship display is a set of display behaviors in which an animal, usually a male, attempts to attract a mate; the mate exercises choice, so sexual selection acts on the display. These behaviors often include ritualized movement ("dances"), vocalizations, mechanical sound production, or displays of beauty, strength, or agonistic ability.
The variable checkerspot or Chalcedon checkerspot is a butterfly in the family Nymphalidae. It is found in western North America, where its range stretches from Alaska in the north to Baja California in the south and extends east through the Rocky Mountains into Colorado, Montana, New Mexico and Wyoming. The butterfly is usually brown or black with extensive white and yellow checkering and some red coloration on the dorsal wing. Adult wingspan is 3.2–5.7 cm (1.3–2.2 in). Adult butterflies feed on nectar from flowers while larvae feed on a variety of plants including snowberry (Symphoricarpos), paintbrush (Castilleja), Buddleja, Diplacus aurantiacus and Scrophularia californica.
Scathophaga stercoraria, commonly known as the yellow dung fly or the golden dung fly, is one of the most familiar and abundant flies in many parts of the Northern Hemisphere. As its common name suggests, it is often found on the feces of large mammals, such as horses, cattle, sheep, deer, and wild boar, where it goes to breed. The distribution of S. stercoraria is likely influenced by human agriculture, especially in northern Europe and North America. The Scathophaga are integral in the animal kingdom due to their role in the natural decomposition of dung in fields. They are also very important in the scientific world due to their short life cycles and susceptibility to experimental manipulations; thus, they have contributed significant knowledge about animal behavior.
Bateman's principle, in evolutionary biology, is that in most species, variability in reproductive success is greater in males than in females. It was first proposed by Angus John Bateman (1919–1996), an English geneticist. Bateman suggested that, since males are capable of producing millions of sperm cells with little effort, while females invest much higher levels of energy in order to nurture a relatively small number of eggs, the female plays a significantly larger role in their offspring's reproductive success. Bateman’s paradigm thus views females as the limiting factor of parental investment, over which males will compete in order to copulate successfully.
Bicyclus anynana is a small brown butterfly in the family Nymphalidae, the most globally diverse family of butterflies. It is primarily found in eastern Africa from southern Sudan to Swaziland. It is found mostly in woodland areas and flies close to the ground. Male wingspans are 35–40 mm and female wingspans are 45–49 mm.
Sexual antagonistic co-evolution is the relationship between males and females where sexual morphology changes over time to counteract the opposite's sex traits to achieve the maximum reproductive success. This has been compared to an arms race between sexes. In many cases, male mating behavior is detrimental to the female's fitness. For example, when insects reproduce by means of traumatic insemination, it is very disadvantageous to the female's health. During mating, males will try to inseminate as many females as possible, however, the more times a female's abdomen is punctured, the less likely she is to survive. Females that possess traits to avoid multiple matings will be more likely to survive, resulting in a change in morphology. In males, genitalia is relatively simple and more likely to vary among generations compared to female genitalia. This results in a new trait that females have to avoid in order to survive.
A nuptial gift is a nutritional gift given by one partner in some animals' sexual reproduction practices.
Sexual selection in scaled reptiles studies how sexual selection manifests in snakes and lizards, which constitute the order Squamata of reptiles. Each of the over three thousand snakes use different tactics in acquiring mates. Ritual combat between males for the females they want to mate with includes topping, a behavior exhibited by most viperids in which one male will twist around the vertically elevated fore body of its opponent and forcing it downward. It is common for neck biting to occur while the snakes are entwined.
Sexual selection in insects is about how sexual selection functions in insects. The males of some species have evolved exaggerated adornments and mechanisms for self-defense. These traits play a role in increasing male reproductive expectations by triggering male-male competition or influencing the female mate choice, and can be thought of as functioning on three different levels: individuals, colonies, and populations within an area.
Sexual selection in amphibians involves sexual selection processes in amphibians, including frogs, salamanders and newts. Prolonged breeders, the majority of frog species, have breeding seasons at regular intervals where male-male competition occurs with males arriving at the waters edge first in large number and producing a wide range of vocalizations, with variations in depth of calls the speed of calls and other complex behaviours to attract mates. The fittest males will have the deepest croaks and the best territories, with females known to make their mate choices at least partly based on the males depth of croaking. This has led to sexual dimorphism, with females being larger than males in 90% of species, males in 10% and males fighting for groups of females.
Cryptic female choice is a form of mate choice which occurs both in pre and post copulatory circumstances when females in certain species use physical or chemical mechanisms to control a male's success of fertilizing their ova or ovum; i.e. by selecting whether sperm are successful in fertilizing their eggs or not. It occurs in internally-fertilizing species and involves differential use of sperm by females when sperm are available in the reproductive tract.
Telostylinus angusticollis is a fly in the family Neriidae of the insect order Diptera. They are typically found on the east coast of Australia near rotting vegetation. Aggregating on the rotting bark of trees such as Acacia longigolia and other trees in New South Wales and southern Queensland. T. angusticollis flies found in the wild have accelerated speeds of development and age of mortality when compared to those in captivity.
