# data[].attributes.body
Abby Sprenger

Gabby Jonker

Joseph Huyser

Jordan Kramer

# data[].attributes.attachment_link.title
Female killer whales run the show. #naturepbs #wildlife #killerwhales #orca #pbs

# data[].attributes.body
Example Video of how honeybees live and how they interact with the environment.

# data[].attributes.headline
Menopause in Honeybees (Kuszewska et al.)

# data[].attributes.subject
Menopause in Honeybees (Kuszewska et al.)

# data[].attributes.body
In queenless honeybee societies, workers can activate their own ovaries and lay unfertilized eggs. Some workers remain sterile and do not activate ovaries due to genetic and environmental conditions. Physiological age also plays a part, as activating ovaries is metabolically costly. In this study, Kuszewska et al. tested whether older workers cease reproduction by removing a queen and comparing ovarian development from different age cohorts. They also looked at same-age cohorts but with a shortened life expectancy due to injury.

# data[].attributes.body
Physiologically older workers have less activated ovaries than younger individuals, indicating that the possibility of workers’ reproduction decreases with workers’ age. This may happen because bees require a minimum of two weeks to activate their ovaries, meaning physiologically older workers can die before producing their own eggs. Additionally, injury further reduces worker survival, but it doesn't make them age faster than normal. Investing energy in helping relatives care for their offspring rather than channelling that energy into one’s own reproduction can positively influence workers’ fitness. These results are consistent with the kin selection explanation for the evolution of menopause and help us understand the effects of relatedness and social cooperation in animals (Kuszewska et al.).

# data[].attributes.body
In high predation areas guppies are more likely to be eaten, especially at younger ages. In low predation areas, guppies have lower risk from predators, especially in early life. Researchers compared guppies from high-predation environments with those from low-predation areas, focusing on three life stages: before reproduction stage, during the reproduction stage, and the post-reproduction stage.

# data[].attributes.body
The figure on the slide before this shows the results for the different groups of guppies in high and low predation areas. The filled bars represent females who died during their normal reproductive period, and the open bars are those who lived longer than expected and had a significant post-reproductive lifespan. The results show that guppies in high-predation zones matured earlier and had longer reproductive lifespans, contributing to an overall increased lifespan. However, there was no significant difference in post-reproductive lifespan between the groups, suggesting that natural selection primarily affects the reproductive phase of life. This research gives evidence supporting theories that post-reproductive lifespan may be non-adaptive in species without strong social support, highlighting how kin selection could be a driving force for post-reproductive life in more social species.

# data[].attributes.headline
Why don't most animals experience menopause?

# data[].attributes.subject
Why don't most animals experience menopause?

# data[].attributes.body
Most animals experience something like menopause if they live long enough, where their ovaries stop producing eggs (oopause). However, in the wild, very few animals reach this old age because of things like predators, disease, or accidents. Most animals cannot experience menopause because they usually die before reaching it (Le Page).

# data[].attributes.headline
Killer Whale (Orcinus orca) post reproductive lifespans

# data[].attributes.subject
Killer Whale (Orcinus orca) post reproductive lifespans

# data[].attributes.body
Male and female orcas have drastically different lifespans. The females can live up to 90 years old but are only capable of reproducing until their 40’s, while males typically only live 30 years but are able to reproduce for their entire lifespan. The second half of the female orcas life is spent raising existing offspring & grandchildren, passing on knowledge of hunting, habitats, and migration patterns (Nielsen, 2023).

Menopause has developed in other species of toothed whales such as: narwhals, belugas, and short-finned pilot whales. It is theorized that toothed whales have developed menopause because of their close and lengthy contact with members of their family, however none of these species live quite as long as female orcas.

# data[].attributes.body
Ending the reproductive capabilities of an individual early seems counter-productive, but the maternal hypothesis is the idea that menopause developed to prevent older females from dying during childbirth. By reducing personal risk of death and consumption of resources, this would actually benefit them because they would be able to invest more time and resources into existing offspring rather than attempting (and failing) to produce more offspring. According to Aime et al. (2017), this hypothesis is not supported in their study.

# data[].attributes.body
The grandmother hypothesis states that grandmothers who have lived past menopause and are able to help raise grandchildren have an evolutionary advantage over those who cannot help raise future generations. This is very similar to kin selection and increases the inclusive fitness of the grandmother due to the increased survival of others who share genetic material with them.

# data[].attributes.body
The embodied capital model is a model that states having a prolonged juvenile period will allow for more time to learn valuable skills, knowledge, and other attributes. This ties into the grandmother hypothesis, since the young have a longer juvenile state it takes more time & effort to raise them. By having grandmothers who are capable of investing in the young, the juveniles are able to take their time to develop and learn important skills.

According to Aime et al. (2017), in simulations where menopause had previously developed, having an increased Post-Reproductive Lifespan leads to higher survival of grandchildren and fertility of children.

# data[].attributes.body
We found that Honeybees, Orcas, and Guppies have a post-reproductive life. A post-reproductive life is only able to happen under certain environmental factors. One study concluded that honeybees show evidence of having decreased reproduction as they grow older. Honeybees are also heavily involved in supporting relatives' offspring instead of raising their own. Another study suggested that kin selection could be a driving force for post-reproductive life in other social species. The final study suggested that either the grandmother hypothesis or the embodied capital model can explain why orcas evolved to have post-reproductive lives. The grandmother hypothesis suggests that post-reproductive females have an evolutionary advantage. The embodied capital model suggests that a longer juvenile lifespan is directly linked to having a post-reproductive life. The grandmothers are able to effectively put time and resources into grandchildren, increasing their survival and fertility.

# data[].attributes.body
Le Page, M. (2023). Do other animals have a menopause? New Scientist, 260(3463), 12. https://doi.org/10.1016/s0262-4079(23)02033-x

Most animals don’t go through menopause. So why do these whales? : Short Wave. (2024, March 22). NPR. https://www.npr.org/2024/03/22/1198909539/menopause-humans-whales-evolution

# data[].attributes.body
Nielsen, M. L. K., et al. (2023). Temporal dynamics of mother–offspring relationships in Bigg’s killer whales: opportunities for kin-directed help by post-reproductive females. Proceedings of the Royal Society B: Biological Sciences, 290(2000), 1–11. https://doi.org/10.1098/rspb.2023.0139

The authors begin by discussing that Bigg’s killer whales spend more than 30% of their adult lives as post-reproductive females. There is evidence that these animals disperse from their mothers around the age of maturity. Because of this, the authors are looking into how the relationships between mother and offspring change overtime, and the opportunity for mothers to help their offspring. Nielsen examines the opportunities for females to gain inclusive fitness benefits and the potential role of kin selection in driving the evolution of post-reproductive life in Bigg’s killer whales. Nielsen et al. studies the population of Bigg’s that ranges from southeastern Alaska to northern California. The collection of photo-identification and life-history on the whales was taken from 1972 to 2020. Each whale was identified by their dorsal fins and unique markings. Sex was determined by morphological differences or genetic testing. The authors concluded that there are social associations between mother and offspring however, strength of the connection depends on the sex and age of the offspring. Sons have a stronger bond than daughters, and mothers tend to help their sons raise offspring. This increases the fitness of the mother and survival of the grandchildren. Some important conclusions are that smaller groups tend to engage in more cooperation than larger groups. This paper is important for understanding how post-reproductive life has evolved.

# data[].attributes.body
Aimé, C., André, J.-B., & Raymond, M. (2017). Grandmothering and cognitive resources are required for the emergence of menopause and extensive post-reproductive lifespan. PLoS Computational Biology, 13(7), 1–20. https://doi.org/10.1371/journal.pcbi.1005631

In the article “Grandmothering and cognitive resources are required for the emergence of menopause and extensive post-reproductive lifespan”, the authors begin by discussing the difference in PRLs (post reproductive lifespans) between male and females of different species, specifically in humans and killer whales. They discuss multiple theories on how this came to be, such as the Grandmother Hypothesis and Embodied capital model. The article then goes deeper into how post-reproductive lives in females allows for them to help future generations grow up and raise children, and this also causes increased fertility for animals still at child-bearing age. The study used 200 simulated populations of an initial size of 1000 to deduce the effects of ecological parameters on Post-reproductive lifespans, such as how these parameters can maximize PRLs, and testing the previously mentioned Grandmother hypothesis and  embodied capital model  to see if they resulted in emergence of menopause and extended post reproductive lifespans. They found that investing in neural development promotes accumulation of skills and experience throughout life, which is beneficial to both the menopausal individual and the young.

# data[].attributes.body
Reznick, D., Bryant, M., & Holmes, D. (n.d.-a). The evolution of senescence and post-reproductive lifespan in guppies (poecilia reticulata). PLOS Biology. https://journals.plos.org/plosbiology/article?id=10.1371%2Fjournal.pbio.0040007

​The article "The Evolution of Senescence and Post-Reproductive Lifespan in Guppies (Poecilia reticulata)" investigates how varying predation pressures influence the lifespan and reproductive patterns of guppy populations. In high predation areas guppies are more likely to be eaten, especially at younger ages. In low predation areas guppies have lower risk from predators, especially in early life. Researchers compared guppies from high-predation environments with those from low-predation areas, focusing on three life stages: before reproduction stage, during the reproduction stage, and the post-reproduction stage. The authors revealed that guppies in high-predation zones matured earlier and had longer reproductive lifespans, contributing to an overall increased lifespan. However, there was no significant difference in post-reproductive lifespan between the groups, suggesting that natural selection primarily affects the reproductive phase of life. This research gives evidence supporting theories that post-reproductive lifespan may be non-adaptive in species lacking social structures where post-reproductive individuals enhance the fitness of relatives.

# data[].attributes.body
Kuszewska, K., Woloszczuk, A., & Woyciechowski, M. (2024). Reproductive Cessation and Post-Reproductive Lifespan in Honeybee Workers. Biology (2079-7737), 13(5), 287. https://doi.org/10.3390/biology13050287

In addition to the nonhuman primates, toothed whales, and guppies, this paper provides evidence to suggest menopause existing in honeybee societies. It begins with describing how, in queenless honeybee societies, workers can activate their own ovaries and lay unfertilized eggs. Some workers remain sterile and do not activate ovaries due to genetic and environmental conditions. Physiological age also plays a part, as activating ovaries is metabolically costly. In this study, they tested whether older workers cease reproduction by comparing ovarian development from different age cohorts as well as same-age cohorts but with a shortened life expectancy due to injury. They first indicated that the workers in different age and treatment groups had different lifespans, then focused on hypopharyngeal glands (HPGs), which produce brood food. In the control group, gland size decreased with age, but this correlation was not found in the injured group likely because they were all at least 15 days old, the age when many already would have transitioned to foraging, which leads to gland degeneration. They then focused on the number of ovarioles and ovary activation and found that older bees and injured workers showed less ovary activation. Workers with a shorter life expectancy (older and injured workers) have a higher probability of dying before their ovaries start to produce eggs, so it is possible they invest energy in helping relatives rather than reproducing themselves. As such, it is proposed that they experience a kind of menopause.

# data[].attributes.body
Outline:

-Introduction: This will introduce our topic and provide information to allow the reader a better understanding. A video will likely be included.

-Body: This will be divided between two group members. Both will focus on providing examples of animals who experience menopause and one person will explain why most animals don't experience it while the other will focus on how it relates to cooperation.

-Conclusion: A short summary will be provided and what further directions can be made with our research found. The importance of this topic will be emphasized, and a video will also likely be added.