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Image of a whale shark near La Paz on the Sea of Cortez. This was taken while Swimming with Whale Sharks.

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Whale Shark Facts and Information - The Details

A whale Shark from my dive trip to the Galapagos Islands

Whale sharks are the largest of the four giant filter feeding elasmobranchs of today. The others are the basking shark, the megamouth shark, and the manta ray. A large adult whale shark can reach up to 60 feet in length. These unmistakable creatures have huge broad heads and wide mouths, are dark gray to black, and have spots covering their bodies. While they are the largest fish in the sea, they are gentle giants that have adapted to a life of filter feeding. Their teeth show this adaptation by being reduced in size to mere millimeters.

Conservation Status

In 2016 the International Union for Conservation of Nature (IUCN) placed whale sharks on the endangered species list. The IUCN Red List cites an overall 60% decline in the Indo-Pacific population and a 30% decline in the Atlantic population. They also state population declines are expected to continue into the future.

The Size of Whale Sharks

Even in scientific literature, there appears to be a wide variation in the reported "maximum" size of whale sharks. This is partly due to the fact that many whale sharks studied are juveniles from aggregation sites, and large adults are seldom seen or studied. McClain et al. has made the best maximum size estimates by sorting through whale shark sizes and measurement methods in the scientific literature. They conclude the largest and most accurately measured whale shark specimen was 18.8 m in length, or 61.7 ft. (McClain et al. 2015). This giant specimen was caught by the whale shark fishery off the coast of India in the Arabian Sea (Borrell et al. 2011).

This certainly doesn't mean the average size of whale sharks are 60 feet, or even 40 feet. From personally reading through piles of scientific whale shark literature, it appears anything over 12 meters (39 feet) is exceedingly rare.

Unfortunately, whale sharks are undergoing a rapid population decline. As the whale shark population declines, they are also becoming smaller in size. Bradshaw et al. reports a 2 m decline in the average size of whale sharks around Australian waters (2008). Larger individuals appear to be targeted more by fisheries, both legally and illegally. So maybe there were many large 60-foot whale sharks in the past, but today it's extremely difficult to find a specimen over 40 feet!

Distribution

Whale sharks are found in warm and temperate waters globally, in the Atlantic, Pacific, and Indian Oceans. Similar to actual whales, whale sharks are highly migratory and can travel thousands of kilometers across oceans. They are normally solitary, but can be found together in seasonal feeding grounds. They may also migrate to birthing grounds in the open oceans (Hueter et al. 2013). Sequeira et al. has found that whale sharks are able to migrate between entire oceans over a few year time period. (Sequeira et al. 2013).

How do whale sharks eat?

Whale sharks are one of the few types of filter feeding sharks. These sharks have modified gill raker structures, or filter pads, along the gills. While swimming, they open their mouths to allow plankton-filled water to flow through the gills. The filter pads along the gills strain out the plankton and small fish. Unlike basking sharks, whale sharks and probably megamouth sharks don't always filter feed; they also suction feed. Suction feeding is where they will suck in a large quantity of water along with their prey. Whale sharks are sometimes seen hovering vertically and suctioning in large clouds of plankton and fish eggs from near the surface. The different types of feeding methods appear to correspond to the type and abundance of zooplankton (Nelson & Eckert 2007).

What do whale sharks eat?

Whale sharks feed on a variety of small prey, including zooplankton, small fish, squid, and fish eggs. They are known to aggregate in large numbers in areas where food is known to be concentrated, or in seasonal fish spawning grounds. There are many of these seasonal whale shark aggregation sites around the globe. Notable sites include:

The Sea of Cortez in Mexico: Here, they congregate to eat Copepods, a type of zooplankton, in the winter months (Nelson & Eckert 2007). Here is an article about Swimming with Whale Sharks in the Sea of Cortez

Around the Yukutan Peninsula in Mexico: Congregations eat Little Tunny fish eggs from spawning events in the summer (de la Parra et al. 2011).

Ningaloo Reef in Western Austalia: They eat zooplankton brought about by the mass spawning of corals in the southern hemispheres fall (Taylor 1996).

Gladden Split of Belize: They eat Cubera Snapper and Dog Snapper fish eggs during the spring spawning events (Graham & Roberts 2007).

Maldives in the Indian Ocean: These islands host resident populations that feed of plankton year round, while small aggregations occur a few different times of the year.

Tiny Teeth

When filter feeding developed in sharks, their teeth, as expected, reduced in size. However, they strangely increased in number. Today, whale sharks have over 300 rows of teeth, with each row having about 1000 teeth. This brings the total number of teeth in a whale shark to over 3000!

This is a picture of a fossil whale shark tooth from the Pungo River Formation, in Aurora, NC.
This fossil was found by Jim Stedman. Image used with permission.

Whale Shark Origins

Filter feeding sharks evolved independently several times, with the earliest appearing in the late Cretaceous with Pseudomegachasma (Shimada et al. 2015). Early whale sharks (PalaeoRhincodon) made their first appearance during either the late Paleoecene or early Eocene. Although reported in the Paleocene Aquia formation (Kent 1994), fossil teeth of the genera PalaeoRhincodon can be found in early Eocene sediments in Africa, Central Asia, Europe, and Eastern North America, including the Nanjemoy in Virginia. These early whale sharks had side cusps on their teeth. By the late Oligocene, around 28 million years ago, the modern whale shark, Rhincodon appeared. The first Rhincodon fossils come from the Chandler bridge formation in South Carolina (Cicimurri & Knight 2009). The teeth underwent slight morphological changes from PalaeoRhincodon teeth, including the loss of the side cusps. By the Miocene, Rhincodon whale shark fossils were found Europe and eastern North America. These Miocene Rhincodon teeth look identical to the living Rhincodon typus teeth and are therefore often called Rhincodon cf typus.

Where to Find Fossil Whale Shark Teeth

Fossil whale shark teeth are very small and uncommon. Therefore, they are difficult to find. In order to find them, one must fine screen sediments from formations where they occur.

Although fossil whale shark teeth have nowhere near the reputation of megalodon teeth, these micro teeth are still sought after by the refined fossil collector. By persistently and meticulously fine screening the Pungo River sediments in front of the Aurora Fossil Museum, these micro whale shark teeth can be found. If one wants more than fossil teeth, the more adventurous can even swim with these gentle giants and experience them first hand.

Image of a whale shark from my Galapagos dive trip.

Recommended Shark Books

Sharks of the World: A Complete Guide

Sharks of the World: A Complete Guide (Wild Nature Press)
Authors: Dr. David A. Ebert, Marc Dando, Dr. Sarah Fowler: 2021

Fully revised and updated, Sharks of the World is the ultimate reference guide for shark enthusiasts. Covering 536 species, it boasts vibrant illustrations, photos, and informative diagrams. The comprehensive guide incorporates the latest taxonomic revisions and offers insights into shark biology, ecology, and conservation. A must-have for any shark enthusiast.

101 American Fossil Sites You've Gotta See

101 American Fossil Sites You've Gotta See
Albert B Dickas, 2018

This is a great updated fossil sites book with at least one fossil site in each state. Each site is broken into 2 pages. One has detailed information, such as directions, GPS coordinates, formation information, etc... The other is dedicated to images of the site and the fossils found there. It also gives information on fossil 'viewing' sites such as dinosaur trackways, museums, and active excavations.
Plus, my fossil photos are peppered throughout this book!

Dinosauria and Prehistoric creatures: Ancient Sharks

Dinosauria and Prehistoric creatures: Ancient Sharks

Shetan Noir's paperback compilation of interviews with leading prehistoric shark experts, including Dr. Shimada, Kent, and Godfrey, offers diverse insights on an array of prehistoric shark topics like Helicoprion jaw structure. Despite minor formatting issues, the large-print book, over 100 pages with vibrant photos, provides a quick, fascinating read. Highly recommended for any prehistoric shark enthusiast. Plus I have a chapter in it!

Borrell A, Aguilar A, Gazo M, Kumarran RP, Cardona L (2011) "Stable isotope profiles in whale shark (Rhincodon typus) suggest segregation and dissimilarities in the diet depending on sex and size." Environmental Biology of Fishes. 92:559-567. (doi: 10.1007/s10641-011-9879-y)

Bradshaw, CJA, Fitzpatrick, BM, Steinberg, CC, Brook, BW and Meekan, MG (2008) "Decline in whale shark size and abundance at Ningaloo Reef over the past decade: The world's largest fish is getting smaller." Biological Conservation 141(7): 1894-1905.

Cicimurri, DJ, and Knight, JL (2009) "Late Oligocene sharks and ray from the Chandler Bridge formation, Dorcheste County, South Carolina, USA." Acta Palaeontologica Polonica, 54, 627-647.

Graham R, Roberts C (2007) "Assessing the size, growth rate and structure of a seasonal population of whale sharks (Rhincodon typus Smith 1828) using conventional tagging and photo identification." Fish Res 84:71- 80

Hueter RE, Tyminski JP, de la Parra R (2013) "Horizontal Movements, Migration Patterns, and Population Structure of Whale Sharks in the Gulf of Mexico and Northwestern Caribbean Sea." PLoS ONE 8(8): e71883. (doi:10.1371/journal.pone.0071883)

Kent BW (1994) "Fossil Sharks of the Chesapeake Bay Region." Egan Rees and Boyer, Inc., Columbia, MD. 146pp.

McClain CR, Balk MA, Benfield MC, et al. (2015) "Sizing ocean giants: patterns of intraspecific size variation in marine megafauna." Peer J, 3, e715.

Nelson JD, Eckert SA (2007) "Foraging ecology of whale sharks (Rhincodon typus) within Bahia de Los Angeles, Baja California Norte, Mexico." Fisheries Research 84: 47-64.

de la Parra Venegas R, Hueter R, González Cano J, Tyminski J, Gregorio Remolina J, et al. (2011) "An unprecedented aggregation of whale sharks, Rhincodon typus, in Mexican coastal waters of the Caribbean Sea." PLoS ONE 6(4): e18994. (doi:10.1371/journal.pone.0018994)

Pierce SJ and Norman B (2016) "Rhincodon typus." The IUCN Red List of Threatened Species 2016: e.T19488A2365291. http://dx.doi.org/10.2305/IUCN.UK.2016-1.RLTS.T19488A2365291.en. Downloaded on 29 November 2016.

Sequeira, AMM, Mellin, C, Meekan, MG, Sims, DW and Bradshaw, CJA (2013) "Inferred global connectivity of whale shark Rhincodon typus populations." J Fish Biol, 82: 367-389. (doi:10.1111/jfb.12017)

Shimada K, Popov EV, Siversson M, Welton BJ, Long DJ (2015) "A new clade of putative plankton-feeding sharks from the Upper Cretaceous of Russia and the United States." Journal of Vertebrate Paleontology 35 (5): e981335. (doi:10.1080/02724634.2015.981335)

Taylor JG (1996) "Seasonal occurrence, distribution and movements of the whale shark, Rhincodon typus, at Ningaloo Reef, Western Australia." Mar. Freshw. Res. 47, 637-642. (doi:10.1071/MF9960637)

Visaggi, CC, & Godfrey, SJ (2010) "Variation in composition and abundance of Miocene shark teeth from Calvert Cliffs, Maryland." Journal of Vertebrate Paleontology v. 30, p. 26-35. (doi:10.1080/02724630903409063)