Whale sharks (Rhincodon typus) are the largest known fish species in the world, and at certain times of the year can be found off the coast of Northern Peru. Many aspects of their life history are still poorly understood, which complicates conservation efforts.
Nonetheless, here are some key facts currently known about whale sharks and how you can incorporate them in a Peru visit:
1. Size:
Whale shark with snorkeler for scale.
Exact sizes are tricky, because measurements at sea are generally based on visual estimates.
A whale shark has been recorded at nearly 19m (62 ft), but the average mature adult is between 7.5 and 9.7m (25 - 32 ft) in length. This translates to a weight of 13.6 to 18.7 metric tonnes (about 30 - 40,000 lbs).
Obviously, juveniles are much smaller, measuring 0.6 to 1.2 m (2 - 4 ft) at birth.
2. Age & Reproduction:
Accurate age determination of whale sharks is also difficult, but studies using growth bands in vertebrae and radiocarbon-dating suggest typical lifespans of at least 70 years, with some individuals likely reaching or exceeding 100 years.
Whale sharks are slow-growing and reach sexual maturity relatively late; females typically mature at larger sizes than males - at around 25 to 30 years of age - which is consistent with long-lived, slow-reproducing species.
Mating and reproductive behaviour are poorly documented in the wild. Some reports describe males following and bumping females, as part of the courtship.
Whale sharks are ovoviviparous - meaning that females give birth to live young from eggs that hatch internally.
3. Appearance:
A whale shark’s overall body shape is broad, cylindrical, and slightly flattened, with a large, wide head and a nearly terminal mouth that can span up to 1.5 m (5 ft) across.
Whale shark with individual markings and scar.
Despite their size, their mouths contain tiny teeth and numerous gill rakers adapted for filter feeding.
Their colouring is bluish-grey / brownish-grey on the dorsal (upper) side, fading to a pale white or cream belly. This helps camouflage them from predators - such as orcas, great white sharks and tiger sharks - and prey.
The skin is thick and rough with dermal denticles (tooth-like scales) that give a sandpaper-like feel.
Each whale shark has unique markings: a distinctive mosaic of pale yellow or white spots, and horizontal and vertical stripes across the back and sides. These markings remain consistent throughout an individual’s life and are used by researchers to identify and catalogue whale shark populations.
Over a whale shark’s lifetime, their skin may accumulate scars from boat strikes or predators.
Whale sharks have two dorsal fins: a larger first dorsal and a smaller second dorsal further back.
Dorsal & pectoral fins and gill slits visible on whale shark.
They have pectoral fins which are large and paddle-shaped, and which aid in steering; while the caudal (tail) fin is semi-lunate (crescent-shaped) and powerful, providing propulsion.
They have large gill slits on each side that extend nearly the full height of the head region and are used in filter feeding when water passes through the mouth.
4. Movement & Navigation:
Whale sharks are highly migratory, with satellite tagging showing migration distances spanning hundreds to thousands of miles, across and between oceans. They move seasonally in response to changes in water temperature, prey availability, and plankton blooms.
They are frequently accompanied by schools of small fish and/or remoras that follow for protection and to feed on leftovers or parasites.
While there is still a lot more research to be done, it is thought that individuals return annually to productive feeding grounds, such as the Ningaloo Coast, Western Australia; Mexico; the Maldives; the Seychelles; the Galápagos Islands and Peru’s coast.
Whale sharks likely use a combination of oceanographic cues, such as temperature fronts and chlorophyll concentration, geomagnetic fields, and olfactory/chemical cues to locate these feeding areas.
As well as this, many whale sharks vertical movement patterns ie spending daylight hours near the surface when feeding and diving deeper at night, or vice versa, depending on prey movement.
5. Behaviour:
Despite their enormous size, whale shark are filter feeders, consuming plankton, nekton, small fish, and squid.
They use a combination of ram filtration (moving forward with an open mouth) and active suction (closing and opening the mouth to draw in water).
Whale shark feeding close to the surface.
They can also adapt their feeding depending on the prey distribution: they feed at or near the surface during plankton blooms, for example, sometimes rolling slightly to one side to maximise intake … but can also feed at depth.
They have well-developed senses of smell and sight, plus electroreception (like other sharks) that may help detect prey and navigate.
Whale sharks are typically solitary, but do congregate at feeding sites - driven by localised, predictable food resources, rather than social bonds.
When whale sharks do come together, there is no evidence of vocalisation: social signaling appears to be visual or tactile during close encounters and courtship.
6. Conservation Status:
Whale sharks are listed as endangered owing to threats including bycatch, vessel strikes, and habitat degradation. The fact that they often feed at the surface increases the risk of collision with boats and entanglement in fishing nets.
Despite it being illegal in most countries, there is also still a trade in whale shark fins and meat, which is highly valued in many Asian countries.
Moreover, whale sharks react to human disturbance by changing depth, swimming speed or by simply leaving the area. It is not really known how this may impact the species health in the long term.
Their large size and migratory habits make accurate population and size assessments challenging, increasing the importance of careful scientific monitoring.
How to see Whale Sharks in Peru:
Whale sharks appear along the Peru’s northern Pacific coast, from the department of La Libertad up to the Ecuadorean border from June to November … with the best sightings usually from July to October. At this time of year, upwelling along the Peru’s continental shelf - where the Nazca Plate meets the South American land mass - brings plankton and small fish that attract the whale sharks.
Whale shark with swimmer near Punta Sal, Piura.
Good places to take a whale shark boat tour include Trujillo, Punta Sal and Mancora. Operators cannot guarantee that they will find these huge fish, but they work with local fishermen for the latest information on where they have been spotted.
Given whale sharks are enormous and yet commonly tolerate human presence, it is on many people’s bucket list to swim with them. For the moment, this is still allowed, but it is important to act responsibly in order to avoid stressing the animals or altering feeding behaviour:
Keep a safe distance
Do not touch
Avoid direct approach
Limit the number of swimmers around the animal
For more information, please get in touch.