Killer Whale Grandmothers Boost Survival of Calves


Along with being one of the world’s most powerful predators, Killer whales are also highly intelligent and social creatures with intricate techniques of interaction. They can be found almost all around the world in highly productive areas of cold water upwelling. They are usually found in ‘pods’ which consist of various sexes and ages. It usually contains the mother and the one or two offspring. The strong associations between the pod members carry on into adulthood, therefore family associations are very strong, where each member has certain roles. This article looks at the effect post-menapausal grandmothers have on their offspring compared to breeding grandmothers. They do this by looking at salmon population data as they believe grandmothers play a large role in collecting prey. 


Besides humans, only 4 species are known to experience menopause: belugas, narwhals, killer whales and short-finned pilot whales. According to one of the authors of the study, Sam Ellis, in killer whales, the reason to stop reproducing is because both male and female offspring stay with the mother for life. If the mother keeps having young, they would have their own descendants competing for resources. Older females share their knowledge in order to help their group survive. Killer whales have “the longest post-reproductive life span of all nonhuman animals: Females stop reproducing in their 30s to 40s but can survive into their 90s.” This allows the mothers to maximize the fitness of her offspring by ensuring their survival and that the offspring achieve reproductive success.

Methods (Models and Variables)

With regard to methodology, this research was comprised of 3 interconnected methods: Study populations, Survival Model with Time-Dependent Effects, and Interbirth Interval Model. In the Study Populations, demographic records were collected manually using photographic censuses for 2 resident killer whale populations: Southern (1976-2016) and Northern (1973-2016) populations in the inshore coastal waters of Washington State and British Columbia, Canada. Individuals were identified by their unique fin shapes, saddle patches, and the presence of any nicks or scratches, and were sexed using distinctive pigmentation patterns around the genital slits and, in adults, differences in fin size. Genealogical relationships were inferred from long-term observations of social organization, and mothers were identified by their repeated association with young calves.

Overall, the Data collected for the analysis was comprised of the following variables: Year of Birth (YOB), Year of Death  (YOD), ID of Mother. The aforementioned variables were used to deduce the Age of Death, and Maternal Grandmother ID in order to provide enough variables to run the models. In the Survival Model with Time-Dependent Effects, a Cox Proportional Hazards model was created to examine the consequences of a grandmother’s death on grand offspring survival. Lastly, an Interbirth Interval Model was used. A Generalized additive model was used to examine the consequences of a grandmother’s status on her daughter’s interbirth intervals. To test whether grandmothers decrease their daughters’ interbirth intervals, the researchers regressed a number of covariates on each interbirth interval. 


Considering the above methods to compile forty years’ of data into a survival model and an interbirth interval model, numerous specific models were considered for each task. The best model for the survival model was given by the following equation which reflects a general grandmother and post-reproductive grandmother effect.


Where sMR is 1 for male, 0 for female (if mother died in past two years) GMR is 1 if grandmother died in past two years, and GMo45 = 1 if grandmother was post-reproductive, slm is salmon index.

From this we see that the loss of a grandmother within the last two years increases mortality hazard by 4.5, while the loss of a post-reproductive grandmother increases mortality by 6.7, if the salmon index is at the norm of 1. If the salmon index is lower (meaning food is scarcer), the grandmother effect becomes even more pronounced. The sex impacted the mother effect, but not the grandmother effect.

The best interbirth interval model demonstrated that living grandmother’s did not impact the interbirth interval for mothers. However, two alternative equations with low AIC relative to the best model, both included grandmother effects on interbirth interval but shockingly showed that the presence of a grandmother tended to increase the interbirth interval of a mother.


The purpose behind menopause has been an evolutionary puzzle, especially as only humans and four species of whales experience menopause. Female killer whales in particular have evolved the longest post-reproductive life span of all nonhuman animals. By demonstrating that post-reproductive grandmothers reduce grand offspring mortality more than grandmother killer whales that are still reproducing, this research reveals the measurable positive influence that menopause has on killer whales’ grand offspring. Knowing the benefits that menopause brings to the killer whales is essential to understanding why female killer whales have evolved to live long lives post-reproduction.

Chosen News Article

University of York. “Killer Whale Grandmothers Boost Survival of Calves.” ScienceDaily, ScienceDaily, 9 Dec. 2019. 


Foster, E. A., Franks, D. W., Mazzi, S., Darden, S. K., Balcomb, K. C., Ford, J. K. B., &
Croft, D.
P. (2012). Adaptive Prolonged Postreproductive Life Span in Killer Whales. Science,
337(6100), 1313.

Imster, E. (2018, August 31). Beluga whales and narwhals go through menopause. Retrieved
February 16, 2020, from

Nattrass, Stuart, et al. “Postreproductive Killer Whale Grandmothers Improve the Survival of Their Grandoffspring.” PNAS, National Academy of Sciences, 26 Dec. 2019, (2010). Orcas: Killer whales are the largest dolphin species. [online]
Available at: [Accessed
17 Feb. 2020].

Robin W Baird and , Hal Whitehead ” Social Organization Of Mammal-Eating Killer Whales:
Group Stability And Dispersal Patterns – Canadian Journal Of Zoology “. 2020. Canadian
Journal Of Zoology.

Yong, E. (2017, January 12). Why Killer Whales (and Humans) Go Through Menopause. Retrieved February 16, 2020, from

Great Barrier Reef decline over the last 90 years and how to save them!



The Great Barrier Reef, home to the largest coral reef system and thousands of species of organisms, faces threats of climate change, pollution, and fishing, bringing its health into great concern. The decline of reefs due to changes in the way they build and the species that inhabit them risk the food and livelihood of hundreds of millions of people. This study examines data collected over the past 91 years to better understand the survival of coral reefs, exploring the documented environmental conditions surrounding coral reefs, community structures of organisms there, and highly accurate mapping of the reef. 



The researchers selected a reef that had been subject to study a number of times in the past, dating back to a quadrat-based survey that ran from 1928 to 1929. They observed coral and marine species biodiversity, supplementing their work with photographs. Areas previously studied were photographed and these photographs edited into one continuous mosaic. Comparing that mosaic (and the species it featured) to reports from previous expeditions allowed the researchers to determine the nature and extent of major trends in the reef.



The barrier reef has seen the worsening of coral cover, colony size, and species diversity over the last 90 years. Coral cover and colony size have declined, with no corals in many intertidal areas named for their dominant reef-building coral. There has been a drastic fall in species richness. Revisiting 13 sites from 1954 found that many species of coral were near extinction and all the sites saw their population decline to half. Corals forms have changed from hard corals to soft corals and from branching corals to massive corals. Many invertebrates that called these intertidal coral colonies home have vanished.


 Figure 1: Dead coral reefs near Low Island



In the past, coral cover has been used as an indicator for reef health as it strongly predicts the capacity of a reef to track sea-level rise and resist drowning. However, species diversity and richness are crucial indicators of reef health. In addition to lower coral cover and size, there has also been a huge drop in species diversity and richness since 1928. This lower diversity is likely as a result of chronic stress and disturbances. These conditions select for coral species which are disturbance resistant and slow-growing, such as soft corals and massive corals. Coral now takes longer to recover following a disturbance such as a cyclone. Additionally, coral reefs which fail to reassemble a diverse community have higher vulnerability and sensitivity to future disturbances. Low Island has failed to reassemble a diverse community and is more susceptible to both drowning and cyclones than it was in the past. Reports since 2000 suggest identical effects in inshore and offshore reefs globally. Hence, the decline of reefs on low isles provides an unfortunate story for coral reefs globally. 


Potential Solutions

Solving the Coral reef problem requires pollution control, better fishing policies, reducing CO2 emissions and extreme temperatures. Better fishing practices improve reef health by preventing overfishing of keystone species crucial to the local ecosystem(Health Fisheries). One example is the decline of shark populations(keystone species) due to overfishing. It has lead to an increase in mid-level feeders, a decline in herbivores and an increase in algae, which harms the coral reefs(Earthsky). Extreme high temperatures due to climate change can potentially destroy 90% of the reefs. Scientists like Daniel Harrison believe that reducing CO2 is insufficient. Instead, they propose reducing reef water temperatures by making clouds brighter and reflecting more sunlight in a process called Marine Cloud brightening(Temple, J.).

Figure 2: Impact of overfishing and loss of species diversity on coral reefs


Figure 3: Mechanism of action of Marine Cloud brightening




  1. Fine, M., Hoegh-Guldberg, O., Meroz-Fine, E. et al. Ecological changes over 90 years at Low Isles on the Great Barrier Reef. Nat Commun 10, 4409 (2019).
  2. Bar-Ilan University. “Longest coral reef survey to date reveals major changes in Australia’s Great Barrier Reef.” ScienceDaily. ScienceDaily, 27 September 2019. <>.
  3. Chemical & Engineering News. “Climate Change Is Destroying Our Coral Reefs. Here’s 3. How Scientists Plan to Save Them.” Accessed February 11, 2020.
  4. Healthy Fisheries. (n.d.). Retrieved from
  5. Earthsky, Researchers find coral reefs at risk when sharks overfished. (n.d.). Retrieved February 12, 2020, from
  6. Temple, J. (2017, April 20). Are brighter clouds the best bet for the Great Barrier Reef? Retrieved February 12, 2020, from

Article Source -Online article Actual Study article references


Earthquakes – They affect marine life, too!

Sperm Whale

Sperm Whale

It seems obvious that earthquakes affect land animals. However, after coming across a National Geographic article on earthquakes and sperm whales, our group became interested in how earthquakes can affect marine megafauna.


Abundant evidence exists demonstrating the effects of earthquakes on land animals. Historical evidence from 373B.C. documents that animals such as rats, snakes, and weasels had abandoned the Greek city of Helios days before an earthquake devastated the place. Anecdotal reports throughout hundreds of years detail similar strange behavior before earthquakes even strike: pet owners have long recorded reports of cats and dogs barking, whining, or showing signs of nervousness before a quake. However, it becomes less clear how these earthquakes may affect marine megafauna.



Sperm Whale Eating Squid Animation

Animation of a Sperm Whale Eating a Squid



         Sperm whales, or Physeter macrocephalus, are a species of marine mammal that can weigh 35 to 45 tons and are typically longer than the average school bus. Sperm whales received their name because they have large quantities of an oily substance called spermaceti in their heads. Although scientists are not completely sure about the purpose of this fluid, some hypothesize that it helps them change their buoyancy as they dive deep for squid and other prey. 

         In November of 2016, a 7.8 magnitude earthquake devastated Kaikoura, New Zealand. Although the number of human casualties was low, it caused complex environmental disturbances. The Kaikoura underwater canyon is one of the few places in the world where you can see sperm whales very close to the shore. The earthquake triggered a series of widespread underwater mudslides in the canyon, causing both powerful currents and changes in water depth relative to sea level. These landslides not only clouded the water, but they also killed or swept away many of the marine invertebrates living in the canyon. These invertebrates are an important source of food for squid and bottom dwelling fish, which are two key prey for male sperm whales. Therefore, scientists hypothesized that the loss and restructuring of marine invertebrates in the Kaikoura canyon would have profound effects on sperm whale feeding patterns. Marine biologist Liz Slooten happened to be studying in the Kaikoura canyon when the earthquake occurred, so she had the chance to directly study the effects of this earthquake. The article emphasizes that such an opportunity is rare in marine research.


Kaikoura Canyon

Kaikoura Canyon

 Results of the study

Using directional hydrophones, researchers tuned into sperm whale breathing sounds and found that post earthquake, male sperm whales spent roughly 25 percent longer at the surface to gather oxygen and rest their muscles. Scientists like Liz Slooten and PhD student Marta Guerra reasoned that this increase in surface breathing resulted because the earthquake swept away marine prey, causing the whales to have to dive deeper and longer to find food. According to the study, before the earthquake, sperm whales foraged in the upper parts of the canyon, but afterwards, they dove to deeper regions. Although this change seems disturbing, one positive note of resilience is that a year after the earthquake, the whales returned to their pre-earthquake breathing patterns. 

 Why are these findings significant? 

         If earthquakes are affecting the abundance and spatial variation of marine life, it is important to understand these effects so that governments can implement appropriate catch and fishing quotas to manage these areas post earthquake.

         Overall, it is clear that while these earthquakes may seem to only be affecting small invertebrates, the movement and death of these invertebrates can have profound trophic cascades. These trophic cascades will affect squid and other fish directly and the large sperm whale predators indirectly.

Additionally, while this study found that sperm whale feeding returned to normal after a year, additional studies should attempt to observe multi-year impacts to understand how earthquakes affect marine ecosystems over long periods of time. 

 Our Chosen Article:  

Rapp, J. L. (2020, January). Earthquakes can make it harder for whales to find food, first-ever study says. National Geographic. Retrieved from

Other References

Mott, M. (2003). Can Animals Sense Earthquakes. National Geographic. Retrieved from

National Geographic. (n.d.). Sperm Whale. National Geographic. Retrieved from

Wagner, E. (2011). The Sperm Whale’s Deadly Call. Smithsonian Magazine. Retrieved from

Melanism in Manta Rays

manta ray

After reading a New York Times article on melanism in manta rays, our group felt inspired to learn more about the species and its interesting condition. For more information, the article is linked here, as well as in the References section!

Background on Manta Rays

There are many organisms of astonishing size in the ocean, but one of the biggest and most magnificent is the manta ray. They are about 25 feet long wing to wing, and due to their extreme size, they have very few predators. There are two different species: the Mobula birostris (the pelagic type) and the Mobula alfredi (the reef type), both of which generally reside in the Indo-Pacific waters. Both species are listed as vulnerable on the IUCN Red List of Threatened Species. When viewed from below, one can observe that most manta rays have a solid white stomach; however, some have unique black spots. These black spots result from melanism—a common condition among land animals but very rare in aquatic animals.

What is Melanism?

Melanism is defined as an increased production of melanin pigments, resulting in darker colored individuals. This is very common on land and has been linked to evolutionary advantages across land animals such as pocket mice, snakes and insects. Underwater, however, melanism is highly uncommon, and out of hundreds of species of cartilaginous fish only two species—both the only known mantas—exhibit melanism. Additionally, melanism exhibited in these mantas only occur in some populations. The variation in melanism frequency in mantas from different locations has caused researchers to wonder if this phenotype provides any evolutionary advantage. 

Melanism and Natural Selection

Melanism in terrestrial animals has proven to be an advantageous result of natural selection. For example, pocket mice in contrastingly light and dark terrain have adapted to match their coat to their surroundings as a means to avoid predators. Beyond camouflage, melanism aids some species in regulating body temperature and resisting disease. Given mantas’ unique development of melanism, researchers aimed to identify which, if any, aspect(s) of fitness it could facilitate. Most manta rays have white bellies, enabling them to blend in with contrasting light from the surface and avoid being seen from below. Though manta rays have few predators, a black belly, or even a spotted one, would presumably make them more prone to predation. Given this hypothesis, marine researchers from the United States, Australia, and Indonesia recently conducted a study to determine whether melanism affects the manta ray’s survival.

Conclusion and Future Work

There is no one definitive answer as to why melanism started to show up in certain manta ray populations around the world. Current studies concluded that melanism does not give mantas survival advantage over their predators; rather, it may just be a product of genetic drift. However, it would be interesting to see a future study on their hunting habits (e.g. time of day), which can help researchers understand if melanism provides an advantage related to when mantas look for their prey. However, future research is increasingly becoming difficult with manta populations dwindling. Nevertheless, it is important to continue to better understand mantas and its important ecological role in the environment.

Ecotourism: The Value of Protecting the Manta Rays

The dwindling populations of Mobula birostris and Mobula alfredi mean their protection and conservation is more important than ever. Off the North Sudanese coast of the Red Sea, high concentrations of reef type mantas frequently congregate in and around Sanganeb Marine National Park and Dungonab Bay – Mukkawar Island Marine National Park. These two sites comprise a marine protected area (MPA) and UNESCO World Heritage Site. In fact, the only documented sighting of a Mobula birostris X Mobula alfredi hybrid ray occurred in this MPA. However, two conflicting proposals may determine the future of the area and the mantas. The Heart of the World, a Dubai-esque proposal including an airport and a huge skyscraper, would involve heavy coastal dredging, increasing turbidity and decreasing plankton abundance—two challenges for the mantas. On the other hand, there’s potential for small-scale ecotourism development based in Mohamed Qol and Dungonab, where manta-watching would promote local economic development while ensuring the MPA stays well protected. Ecotourism is rising across the world and has already shown promise in Sudan. Promoting such practices will provide the best protection for the mantas, facilitating further research into melanism and many other phenomena we’ve yet to discover.   



Augliere, B. (2020 Jan 8). For Manta Rays, Survival Isn’t Black and White. Hakai Magazine.

Kessel, S. T., Elamin, N. A., Yurkowski, D. J., Chekchak, T., Walter, R. P., Klaus, R., Hill, G., & Hussey, N. E. (2017). Conservation of reef manta rays (Manta alfredi) in a UNESCO World Heritage Site: Large-scale island development or sustainable tourism? PLOS ONE, 12(10), e0185419. doi: 10.1371/journal.pone.0185419

Klein, J. (2019 Oct 14). The Mystery of Melanistic Manta Rays. New York Times Science. 

Márquez, M. C. (2019 Dec 26). It’s Not All Black and White: Melanism in Manta Rays. Forbes

Murray, A. (2019 Sept 15). Protecting the Million-Dollar Mantas. Save our Seas.Venables, S., Marshall, A., Germanov, E., Perryman, R. & Tapilatu, R. (2019 Oct 9). It’s not all black and white: investigating color polymorphism in manta rays across Indo-Pacific populations. The Royal Society Publishing. 100(9). 5268-73. doi: 10.1073/pnas.0431157100

Whale Sharks and Manta Rays: Impact of Plastic Pollution in Indonesian Waters

Indonesia in the Coral Triangle region is one of the few locations where concentrated populations of whale sharks and manta rays reside according to Noun Project’s study of their habitats. These filter-feeders help control plankton abundance and regulate nutrient cycling, playing an important role in the marine ecosystem. Unfortunately for the giant mammals, Indonesian waters are alarmingly susceptible to plastic pollution from nearby coastal countries, many of which are ranked in the top 10 for plastic waste. Over time, plastic debris in the sea gets broken down into tiny pieces of plastics less than 5 mm. These so-called “microplastics” are commonly ingested by marine animals and contain pollutants at a concentration that is millions of times higher than the surrounding water. Whale sharks and manta rays are particularly prone to plastic ingestion, as they feed by filtering enormous amounts of water every hour.

In an attempt to determine the vulnerability of large filter feeders to microplastic ingestion, scientists assessed the waters of their typical Indonesian habitats such as those by Nusa Penida, Komodo National Park, and East Java. They studied the top 50 cm of the water column using a plankton net (called a “trawl survey”) and also recorded the visibility of plastic debris from the ocean’s surface. Using this information and the water filtration rates of the two species, they estimated the rate of plastic ingestion. Reef manta rays may ingest up to 63 pieces of plastic per hour when they feed in Nusa Penida and Komodo National Park while whale sharks could be ingesting 137 pieces per hour in Java, where they seasonally aggregate. Additional testing revealed that manta ray and whale shark excrement contained plastics, providing further evidence of microplastic ingestion and accumulation in the fish species. Ingestion of plastics can expose the long-lived animals to toxic chemicals, which can accumulate over decades and harm their regular growth, hormones, and reproductive functions. 

Manta rays and whale sharks are both globally threatened species. Along with reproductive dangers from microplastics, both species face extreme pressures from overfishing. Manta rays have an average lifespan of 40 years while whale sharks have a lifespan of 100 to 150 years; however, because both fish species reproduce slowly and reach sexual maturity much later in life (15 years for manta rays and 30 years for whale sharks) they are being forced out of the ocean faster than they can reproduce. A national effort to reduce and manage plastic waste is essential for the conservation of these marine megafaunas. 

One solution is to use less single-use plastic, such as plastic bags and food wrappers, which are the most abundant plastic sources of the region. The Indonesian island of Bali, known for its tourism, imposed a ban on single-use plastics in July 2019. The island generates more than 300,000 tons of plastic each year, with 11% ending up in waterways. While large shopping centers have ceased providing single-use plastics resulting in a significant reduction in the island’s plastic use, smaller businesses have failed to comply. Thus, imposing stricter penalties and extending this ban to the wider nation will be an effective solution.

Another solution is improving waste management techniques. In November 2019, Ecowatch launched a project to build 100 trash booms in Balinese rivers, a measure meant to eliminate 80% of marine plastic that comes from streams. While these booms are effective at catching debris, the removal of collected waste has proved to be more difficult. Due to the lack of waste facilities on less populated islands, most recyclables must be shipped to Java for processing. This decreases the financially lucrative aspect of trash clean-up. What’s more, due to highly irregular routes and general inexperience, large portions of Indonesia remain unserviced by waste workers. To combat this problem, the Gringogo Indonesia Foundation created an app that will allow civilians to scan garbage and determine its monetary value. Upon its introduction in Sanu Kajar, Bali, this app improved recycling rates by 35% and decreased ocean plastic deposits by 25%. Applying this app to dispose of plastic waste in trash booms has the potential to be an effective waste management solution.


News Article:



“Microplastics on the Menu of Manta Rays and Whale Sharks.” Marine Megafauna Foundation,


Ecowatch. “100 Trash Barriers to Be Installed in Bali Rivers to Reduce Plastic Pollution.” Make a Change World, 25 November, 2019,


Elitza et al. “Microplastics on the Menu: Plastics Pollute Indonesian Manta Ray and Whale Shark Feeding Grounds”. Frontiers in Marine Science, 19 November 2019,


Javerbaum, Molly. “To reduce plastic waste in Indonesia, one startup turns to AI.” The Keyword, July 9, 2019,


“Manta Ray Habitat Map by SEEtheWILD Wildlife Conservation Travel.” Manta Ray Habitat Map by SEEtheWILD Wildlife Conservation Travel, 11 Nov. 2017,


“Many Threats for Manta Rays.” Defenders of Wildlife,


“Meet the Innovators Battling Plastic Waste in Indonesia: Mohamad Bijaksana Junerosano.” World Bank,


“Not the Last Straw Yet: Bali’s Ban on Single-Use Plastics.” South China Morning Post, 12 Nov. 2019,


“View Current Whale Shark Map and Habitat Range.” View Current Whale Shark Map and Habitat Range, 10 July 2019,


Wamsley, Laurel. “A Massive Floating Boom Is Supposed To Clean Up The Pacific. Can It

Work?” NPR, 11 September, 2018,


“Whale Sharks, Rhincodon Typus.” MarineBio Conservation Society, 


“Whale Shark Information.” Shark Team One,