Polyandry in animals
Polyandry also occurs in some primates such as marmosets, mammal groups, the marsupial genus' Antechinus and bandicoots, around 1% of all bird species,[citation needed] such as jacanas and dunnocks, insects such as honeybees, and fish such as pipefish.
Polyandry has direct benefits for females allowing fertilization assurance, provision of resources, and parental care for their offspring.
[5] In a meta analysis, including 10 different orders of insects, polyandry increased the production of eggs by females specifically in Lepidopterans and Orthopterans.
Through polyandry and long-term sperm storage, recent studies have found evidence for the ability of female tortoises to produce clutches of eggs that demonstrate multiple paternity.
[10] As a result of clutches with greater variation in paternal genes and increased sperm competition, females can maximize both the genetic quality and number of offspring.
[11] Multiple paternities within a single clutch is therefore considered an effective strategy to increase the reproductive success and fitness of female tortoises.
[12] As opposed to polygyny, where it has been observed that polygynous females that lay a large number of eggs exceeding the optimal clutch size reduces the fitness of the group.
[14] Snow and Andrade (2005) concluded that the redback spider (Latrodectus hasselti) increases their ability to manipulate the paternity of their offspring by using the spermathecae to store multiple sperms.
Additionally, a study on leaf-cutting ants (Acromyrmex echinatior) supported the hypothesis that sperm mixing indeed occurs in polyandrous social insects.
[14] According to Gordon G. Gallup, as a form of adapting to multiple mating in females, human penile shape is indicative of an evolutionary history of polyandry.
[16] In the polyandrous system, sexual coercion has been observed to be one of the major reasons for why females begin to mate with multiple males to outweigh the cost under different circumstances.
[25] Females that mate with more than one male obtain the aid of both and as a result of all three parents providing food and care to the offspring there is an increase in the survival of their young.
For males, such factors can promote an increase in reproductive success, leaving behind the cost of paternity share (Mating Systems, p277).
[18] However, Lee and Hayes (2004) have evidence that suggests that there is no set data in green turtles that significantly shows that there are potential fitness gains through polyandry.
Both Wright[4] and Lee and Hayes studies exhibit similar results that show a lack of support of the indirect benefits of polyandry.
[19] Current research suggests that polyandry is the dominant social structure in the New World monkey family Callitrichidae.
[34] Unlike most primates who typically give birth to single young, twins are the average litter size for tamarins and marmosets.
The entire group participates in raising the offspring, sharing the responsibilities of infant carrying, feeding, and grooming.
The presence of nonreproductive helpers appears to be the most important factor in determining which mating system is used, as ecological and environmental variability have not been found to have a significant impact.
Indeed, in studies of Saguinus fuscicollis, common name saddle-back tamarin, no monogamous lone pairs have ever been seen to attempt a breeding cycle.
