All You Can Eat

Many people mistakenly imagine that sharks are not picky eaters at all - that they prowl the seas searching for anything and everything to devour. Whilst this is generally not the case for the vast majority of the 550+ species of sharks, even a broken clock is right twice a day and there are, indeed, some sharks that are not selective eaters at all. The most famous example is the tiger shark (Galeocerdo cuvier), which has earned the nickname as the garbage can of the seas. So what do tiger sharks eat? How are they able to have such a broad diet? And are all the crazy rumous of bizarre, man-made objectes being found in their stomachs really true?

Tiger sharks have earned the nickname as the garbage cans of the seas (Image Credit: lego 19861111 / Shutterstock

You're Spiralling

One thing sharks all have in common is that they are carnivores; they eat meat to obtain the energy that they need to move and grow. Therefore, sharks have a gut that is specially adapted to digest the bodies of other animals: muscles, fat, skin, scales, bones, teeth... even feathers, and all! (Madkour et al, 2026).

From the mouth, a shark's food moves through their digestive system vis the stomach, spiral valve and rectum, before exiting through the cloaca (Slough, 2008)

Whilst they can shear their prey into bite-sized pieces, sharks do not chew their food. Therefore, the stomach is the first place that sharks actually start to digest their prey into smaller pieces. Lined with folds called "rugae" and uniquely J-shaped, sharks' stomachs are capable of expanding enormously, to accommodate large feeds. These meals can then remain sitting in the stomach for extended periods. With hydrocholoric acid between pH 1 and 2, sharks' stomach acids are even more acidic than our's; capable of breaking down bones, shells and even some metals. Whatsmore, the strong muscles in the stomach wall continually contract to crush large food items down into mush called "chyme", for digestive enzymes, like pepsin, to then take over digesting (Abel & Grubbs, 2020; Leigh et al, 2021; Madkour et al, 2026).

Sharks have a specialised organ within their digestive system, called a spiral valve, that has evolved to slow the progress of food - maximising how much can be absorbed, despite the guts being relatively short (Image Credit: Haplochromis / WikimediaCommons)

The next step is for chyme to move into the intestines. Unlike the human digestive system, the gut of a shark is actually surprisingly short. Where our intestines have evolved to twist around in order to maximise the length and surface area within the intestines where food can be absorbed, sharks have taken a different approach... Instead of having a long gut, they have instead evolved to simply slow the rate at which food moves through. This is possible thanks to a specialised digestive organ called the "spiral valve". This remarkable scroll-shaped organ increases surface area, ensures one-way through-flow, and helps to avoid hardened objects (like spines or bones) becoming stuck in the digestive tract, but most importantly, it slows the flow of food through the gut, ensuring ample time for the absorption of nutrients (Leigh et al, 2021).

Tiger sharks are the second largest predatory sharks after great whites; with mature females reaching some 5.5 metres from nose to tail (Image Credit: Daniel Torobekov / Pexels)

You Make Me Sick!

Whilst the spiral valve is very tough and can handle sharp, hard objects in their food, tiger sharks have evolved an additional, nifty mechanism that makes their guts especially resilient; they can evert their internal digestive organs to clean them out in the seawater. This sounds bizarre, but bear with me...

Some sharks (like this mako) can evert their stomachs; spitting their inside-out stomach out of their mouth to discharge the contents (Brunnschweiler et al, 2011).

What this means is that tiger sharks can effectively vomit their stomachs out of their mouths and/or can push their spiral valves out of their back ends, in order to rinse out any hard objects that cannot be digested. As a result they can easily deal with beaks, bones, spines, shells and any other hard-parts from their prey, without these blocking their gut; causing pain, illness or even death (Crow et al, 1990; Andrzejaczek et al, 2024).

This allows these animals to be able to take any and all prey that comes across their path, without having to worry about being at all selective (Crow et al, 1990; Abel & Grubbs, 2020; Andrzejaczek et al, 2024).

Tiger shark's uniquely flexible, square- shaped jaws and biserrated, backwards-leaning teeth, make for a strong bite force and uninterrupted cutting edge (Image Credit: Nurture / iStock)

Bite Me!

Tiger sharks have a remarkably powerful bite; with their bite force can ranging from 700 up to 1300 psi - enough to pierce through the hardened shells of seaturtles (Abel & Grubbs, 2020).

Tiger sharks have dually serrated, backwards-leaning teeth, that make a continuous cutting surface against their prey (Image Credit: Stefan Kuhn / WikimediaCommons)

This is not the highest bite force of any animal, or even any shark, but what makes their bite unique is the structure of their mouths. Firstly, their unusual dentition. Tiger Sharks’ teeth are serrated on both sides and lean backwards in their mouths, so that the tips point backwards. Unusually for sharks, all the teeth are similar, including those in both the upper and lower jaws. In addition, the make-up of the cartilage in thier jaws is subtley different to many species, so their jaw bones are actually slightly flexible. This does not make them weak - on the contrary, it ensures that when tiger sharks bite down, the flex in their bones allows the teeth to form an almost completely uninterrupted cutting edge; perfect for sawing and shearing through flesh, bones and... basically... anything that they fancy having a go at (Abel & Grubbs, 2020).

I'll Try Anything Once

Studies from around the world show that tiger sharks are generalist, opportunistic feeders, that eat a wide range of prey (Dicken et al, 2017).

Today scientists have described more that 550 different species of sharks, all of which have evolved unique physiologies, specialised feeding ecologies, and advanced behavioural repertoires that allow them to perfectly fit their ecological niche. Whilst the vast majority of shark species have slowly evolved to become focused on specific prey types, tiger sharks are unique; in that their adaptations have allowed them to reduce specificity in their feeding choices. This means they have the broadest diet of all sharks (Abel & Grubbs, 2020).

Tiger sharks in South Africa were been found with a) small antelope known to locals as a blue duiker, b) humpback dolphin, C) African penguin and skate egg cases, and d) various seabirds in their stomachs (Image Source: Dicken et al., (2017).

Stomach contents studies have revealed that tiger sharks' eat all sorts of other sharks and rays, many different types of boney fishes, reptiles - such as turtles- mammals - like seals and dolphins - squids, octopi, and all sorts of shellfish and crustaceans - bivales, lobsters, crabs and so on. They are also known to eat seabirds, and terrestrial mammals, including livestock, that have wandered or fallen into the ocean. They are true generalists and optimistic predators; often scavenging a large proportion of their diet, rather than bothering to actually hunt and chase their prey (Lowe et al, 1996; Dicken et al, 2017; Abel & Grubbs, 2020).

Tiger sharks are generalist predators that have a very broad diet (Image Credit: Carlos Grillo / Shutterstock)

Plastic Fantastic

A fisher in Australia shared a shocking video to social media, showing several plastic bags being pulled from the stomach of a baby tiger shark (Images Sourced: trapman_bermagui / Instagram)

Tiger sharks live up to their monicker as the 'garbage eaters', as they are often also found with many different man-made objects in their stomachs; clothing and shoes, tyres, metal cans, plastic containers, a chicken coup, and once, even an entire suit of armour, have been swallowed by these unfussy eaters (Lowe et al, 1996; Dicken et al, 2017).

Their ability to evert their stomach and gut is what allows these sharks to swallow such fare; if their body cannot handle breaking it down, they simply eject it back out. But in recent years, tiger shark's indiscriminate snacking has lead to some novel issues... the ingestion of plastics. Studies have found massive amounts of plastics and microplastics in tiger shark's guts - as many as 1603 man-made particles in one specimen! This is significantly higher plastic contamination than we see in many other species of sharks (Munno et al, 2024).

"The high occurrence and abundance of anthropogenic particle contamination in tiger sharks is likely due to their generalist feeding strategy"

Munno et al, 202

The problem with this is that we cannot be sure what effects this might have on these sharks. Are they able to digest all these plastics? Can they eject them via eversion? Do they get absorbed into their tissues? If so, it is likely that these chemicals would have some health impacts, such as hormonal disregulation, which could affect their ability to breed (Ruidas et al, 2024).

Tiger sharks are remarkable creatures, with one of the most impressively well-adapted digestive systems in the natural world, but their populations are declining, so it is vital that we do not cause any additional pressure on their ability to survive and thrive (Ruidas et al, 2024; IUCN, 2026).

Sure it's cool and very impressive that tiger sharks are able to eat metal objects like license plates, tyres and suits of armour, but is it ethically right that they do?

Juvenile tiger sharks are bottom feeders, so they are very likely to ingest marine debris and litter that sinks to the ocean floor (Image Credit: Samual J Coe / Getty Images)

References

Abel D & Grubbs D (2020). Shark Biology and Conservation: Essentials for Educators, Students, and Enthusiasts. Johns Hopkins University Press, USA.

Andrzejaczek S, Gleiss A, Lear K, McGregor F, Chapple T & Meekan M (2024). Stomach eversion and retraction by a tagged tiger shark at Ningaloo Reef, Western Australia. Fisheries research, 269, 106875. Access online.

Brunnschweiler JM, Nielsen F & Motta P (2011). In situ observation of stomach eversion in a line-caught Shortfin Mako (Isurus oxyrinchus). Fisheries Research, 109. Access online.

Crow GL, Howe JC, Uchida S, Kamolnick S, Wisner MG & Caira JN (1990). Protrusion of the valvular intestine through the cloaca in sharks of the family Carcharhinidae. Copeia. Access online.

Dicken ML, Hussey NE, Christiansen HM, Smale MJ, Nkabi N, Cliff G & Wintner SP (2017). Diet and trophic ecology of the tiger shark (Galeocerdo cuvier) from South African waters. PloS one, 12:6, e0177897. Access online.

IUCN (2026). International Union for the Conservation of Nature Red List of Threatened Species; Tiger shark (Galeocerdo cuvier). Accessed 18.02.2026, 08:15am GMT. Access online.

Leigh SC, Summers AP, Hoffmann SL & German DP (2021). Shark spiral intestines may operate as Tesla valves. Proceedings of the Royal Society B: Biological Sciences, 288:1955. Access online.

Lowe CG, Wetherbee BM, Crow GL & Tester AL (1996). Ontogenetic dietary shifts and feeding behavior of the tiger shark, Galeocerdo cuvier, in Hawaiian waters. Environmental Biology of Fishes, 47:2, 203-211. Access online.

Madkour FA, Mohammed ES, El-Nahass EE, Elwan MM, Mohammad AS & Abdelhakeem F (2026). Insights into the stomach of Tiger Shark, Galeocerdo cuvier (Péron & Lesueur, 1822): Histochemical, ultrastructural, and phylogenetic analysis. Tissue and Cell, 103319. Access online.

Munno K, Hoopes L, Lyons K, Drymon M, Frazier B & Rochman CM (2024). High microplastic and anthropogenic particle contamination in the gastrointestinal tracts of tiger sharks (Galeocerdo cuvier) caught in the western North Atlantic Ocean. Environmental Pollution, 344, 123185. Access online.

Ruidas H, Bora G, Dsouza S & Shanker K (2024). Effects of Microplastic Pollution on the Reproductive Organs of the Spadenose Shark, Scoliodon Laticaudus, in Malvan, India. Malvan, India. Access online.

Slough L (2008). Histology of the Digestive System of Scyliorhinus retifer, the Chain Catshark. Access online.