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Life Science,

Thirsty for Blood

Meet five creatures that feast on blood

By Alessandra Potenza
From the October 2020 Issue

Learning Objective: Describe and model the body structures that let bloodsucking animals successfully obtain food.

Lexile: 910L; 560L
Guided Reading Level: S
Focus Area: Adaptations,
Standards
  • NGSS: Core Idea: LS4.C CCSS: Writing: 7 TEKS: Science: 3.10A; 4.10A; 5.10A; 6.12D; ELA: 3.12B; 4.12B; 5.12B; 6.11B

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You’ve probably seen vampires in movies or video games. But bloodthirsty creatures exist in real life too! About 30,000 species of animals feast on blood, including insects, birds, mammals, and fish. 

Blood isn’t hard to find—it pumps through the bodies of all kinds of animals. “But there are many adaptations animals need to feed on blood,” says Sebastian Kvist, a biologist at the Royal Ontario Museum. For instance, bloodsucking creatures have special body parts to pierce the skin of other animals and draw blood. Many also have chemicals in their saliva called blood thinners that keep blood from clotting as they feed.  

Here are five animals that feed on blood—and how they get their liquid meals!

You’ve probably seen vampires in movies. But bloodthirsty creatures exist in real life too! About 30,000 animal species drink blood. They include insects, birds, mammals, and fish.

Blood isn’t hard to find. It pumps through all kinds of animals’ bodies. “But there are many adaptations animals need to feed on blood,” says Sebastian Kvist. He’s a biologist at the Royal Ontario Museum. Bloodsucking creatures have special body parts. They use them to pierce other animals’ skin. Many creatures that drink blood also have chemicals in their spit. They’re called blood thinners. The chemicals keep blood from clotting as the animals feed.

Here are five animals that feed on blood. Learn how they get their liquid meals.

Paulo Oliveira/Alamy Stock Photo

Sea lampreys have a rough, bony tongue to pierce the flesh of other fish.

Sea Lampreys

USGS

The monstrous mouth to the left belongs to a sea lamprey. This fish lives in the Great Lakes as well as the Atlantic Ocean along the coasts of Europe and North America. 

Young lampreys eat algae. But after a few years, the fish become parasites. Adults have a round mouth lined with hundreds of teeth. They use these teeth to grip the skin of trout, salmon, or perch for weeks at a time. They drill a hole in the fish using a bony tongue and drink its blood.

In the ocean, lampreys don’t usually kill their hosts. But the smaller lake fish often die after a lamprey attack. In the Great Lakes, one lamprey can kill 18 kilograms (40 pounds) of fish a year!

The mouth to the left belongs to a sea lamprey. This fish lives in the Great Lakes. It’s also found in the Atlantic Ocean along the coasts of Europe and North America. 

Young lampreys eat algae. But the fish grow to become parasites. An adult has a round mouth. It’s lined with hundreds of teeth. They grip other fish’s skin like trout, salmon, or perch. The lamprey latches on for weeks. It drills a hole in the fish using a bony tongue. Then it drinks the fish’s blood. 

Lampreys don’t usually kill their hosts in the ocean. But smaller fish in lakes often die after a lamprey attack. One lamprey can kill 18 kilograms (40 pounds) of fish a year in the Great Lakes!

Dietmar Nill/Naturepl.com

A vampire bat feeds on blood from a bird’s foot.

Vampire Bats

Some people think that all bats drink blood. But only three species of bats out of 1,400 do. They’re called vampire bats, and they live in Central and South America.  

Like all bats, vampire bats can fly. But they have longer thumbs on their wings than other bats. That lets them quietly creep across the ground and onto the feet of cows, horses, and birds. The bats then use heat-sensing skin around their nose to detect warm blood. They make a cut with their teeth and lap up blood with their tongues. 

As vampire bats feed, their kidneys quickly absorb water from the blood, causing the bats to pee. That makes them less bloated, so they can fly away fast!

Some people think all bats drink blood. But only three out of 1,400 species do. These vampire bats live in Central and South America.

Vampire bats can fly like all bats. But they have longer thumbs on their wings. That lets them creep across the ground. They crawl onto the feet of cows, horses, and birds. The bats have heat-sensing skin around their noses. It can detect warm blood. The bats cut into animals’ skin with their teeth. Then they lap up blood.

Bats’ kidneys quickly soak up water from the blood. This happens as it feeds. It causes the bats to pee. That makes them lighter. So they can fly away fast!

skeeze/Pixabay

Some species of mosquito release droplets of warm blood as they feed to keep cool.

Mosquitoes

You’re probably familiar with this bloodsucker. But did you know that only female mosquitoes drink blood? These blood meals allow the insects to produce eggs.

A mosquito finds humans and other animals by using its antennae to detect the carbon dioxide gas they breathe out. The mosquito then uses its mouth, which is made of six needles, to pierce their skin and suck blood for a few seconds. During its meal, the insect injects its victims with saliva containing blood thinners. Your body reacts by releasing chemicals that make the bite super itchy!

Mosquito saliva can carry viruses and parasites. Diseases spread by mosquitoes kill millions of people a year. That makes the bug the world’s deadliest animal.

You likely know this bloodsucker. But did you know only female mosquitoes bite? Drinking blood allows the insects to make eggs.

A mosquito has antennae. They allow the insect to find humans and other animals. The antennae sense carbon dioxide gas the animals breathe out. A mosquito’s mouth is made of six needles. They pierce an animal’s skin. The insect sucks blood for a few seconds. It also injects its victims with blood thinners. Your body reacts by producing chemicals. They make the bite super itchy!

Mosquito saliva can carry viruses and other germs. Diseases spread by mosquitoes kill millions of people a year. That makes the bug the world’s deadliest animal.

Shutterstock.com

A practitioner squeezes blood out of a leech used for treatment in India. 

Leeches

Yawar Nazir/Getty Images

A practitioner squeezes blood out of a leech used for treatment in India.

Leeches are worms that live in ponds and oceans on every continent. These parasites 

drink the blood of animals like birds, fish, and even humans! 

Most leeches have round mouths with three jaws and up to 300 sharp teeth. They attach their mouths to the skin of a host and move their jaws side to side to make a cut. Leeches usually suck blood for 45 minutes, but some stay on their hosts for weeks. Super-stretchy skin lets the worms draw up to 10 times their weight in blood.

These adaptations make leeches useful in medicine! Some leeches are used to treat diseases and increase blood flow after certain surgeries. The powerful blood thinners in their saliva have been used to make medications.

Leeches are worms. They live in ponds and oceans. They’re found on every continent. These parasites drink animals’ blood. Those animals include birds, fish, and even humans!

Most leeches have round mouths with three jaws. They also have up to 300 sharp teeth. Leeches’ mouths attach to the skin of a host. Their jaws move side to side to make a cut. Leeches usually suck blood for 45 minutes. Some stay on their hosts for weeks. Leeches have stretchy skin. It lets them drink up to 10 times their weight in blood.

These adaptations make leeches useful in medicine! Some doctors use leeches to treat diseases. The worms also help increase blood flow after surgeries. Leeches’ spit contains powerful blood thinners. It’s used to make medicines.

Jonagreen/Dreamstime.com

The vampire finch has a razor-sharp beak to pierce the skin of large seabirds.

Vampire Finches

Jaime A. Chaves

Vampire finches line up and wait their turn to drink the larger seabird’s blood.

Vampire finches are fist-sized birds that live on two of the Galápagos islands in the Pacific Ocean. They normally eat seeds and insects. But when those run low, they feed on the blood of other birds!

The finches work together to attack large seabirds. One finch hops on the seabird’s back and pecks at its skin to make a wound. Other finches wait for their turn. They don’t drink enough blood to harm their victims.

The blood diet gives vampire finches an edge over other finch species when food is scarce. As a result, vampire finches are the most numerous finches on the islands.

Vampire finches are fist-sized birds. They live on two of the Galápagos Islands. They’re found in the Pacific Ocean. The birds normally eat seeds and insects. But sometimes those run low. Then the finches feed on the blood of other birds!

The finches work together. They attack seabirds. One finch hops on the bird’s back. It pecks at its skin to make a wound. Other finches wait for their turn. They don’t drink enough blood to harm their victims.

The blood diet helps vampire finches when food is scarce. It gives them an edge over other finches. That’s why there’s more vampire finches on the islands.

Continue Your Learning

You read about different animals that feed on blood. Take a look at the photos again and think about what you just read. Create a video or poster to share your five favorite facts from the article!

You read about different animals that feed on blood. Take a look at the photos again and think about what you just read. Create a video or poster to share your five favorite facts from the article!

Continue Your Learning

You read about different animals that feed on blood. Take a look at the photos again and think about what you just read. Create a video or poster to share your five favorite facts from the article!

You read about different animals that feed on blood. Take a look at the photos again and think about what you just read. Create a video or poster to share your five favorite facts from the article!

video (1)
Activities (2)
Skills Activities
Quizzes (1)
Answer Key (1)
video (1)
Activities (2)
Skills Activities
Quizzes (1)
Answer Key (1)
Step-by-Step Lesson Plan
Download the Lesson Plan

1. ENGAGE

Use a video to introduce the idea of animal adaptations.

  • Share the video “Amazing Adaptations” with students.
  • Create a chart with three columns labeled: Animal, Adaptation/Characteristic, and Purpose. Use animals from the video to complete the chart collaboratively, with students sharing their responses. Then identify which adaptations help the animals find food. (for example, bats’ ears and lizards’ tongues)
  • Ask: What adaptations help humans find and eat food? (hands to hold farming tools or pick fruit; brains to invent better farming methods; teeth to chew meat and other foods, etc.) What adaptations help animals find and eat food? (keen vision, hearing, or sense of smell; behaviors like hunting in packs)

2. EXPLORE

Read the article and explain the purpose of different adaptations.

  • Preview the article with students, focusing on the photos. Explain that all of these animals feed on blood. Ask students to make predictions about what adaptations help them feed.
  • Read the introduction on page 10 aloud. Ask: What is “clotting”? (when liquids like blood get thicker) Why is it important for some bloodsuckers to have saliva with chemicals that prevent blood from clotting? (If blood clots, it won’t flow as easily, so it will be harder to drink the blood.)
  • Continue reading aloud about each animal, summarizing the key adaptations after each section. Add information about the animals to the chart described in Step 1.
  • Have students reflect on the animals in the article with the Learning Journey at the end of the online article.

3. EXPLAIN

Model adaptations that would allow an animal to feed on blood.

  • Tell students they are going to design hands-on models to see how different animals use different mouthparts to feed on blood. Distribute the skills sheet “Get to the Blood!” After they have completed the hands-on activity, have students share their “vampires” and explain how their animals gather blood. Ask: Do you see any connections with the animals in the article? Discuss how their models represented real animals.

4. EXTEND

Research another animal’s adaptations to get food.

  • Have students research another animal’s adaptations for getting food with the skills sheet “Animal Adaptations Report.” Remind students that adaptations are connected to an animal’s body parts or behavior and help the animal get food, find shelter, and avoid predators.

5. EVALUATE

Demonstrate comprehension with a short, low-stakes assessment.

  • Evaluate students’ understanding by having them complete the “No-Sweat Bubble Test.”

At-Home Ideas

Encourage students to share photos of the “vampires” they created in your virtual classroom (Step 3). Students can discuss their No-Sweat Bubble Test answers in small groups before submitting their Google Quiz (Step 5).

Encourage students to share photos of the “vampires” they created in your virtual classroom (Step 3). Students can discuss their No-Sweat Bubble Test answers in small groups before submitting their Google Quiz (Step 5).

⇨ Learning Journey: Take a look at the photos in the article again and think about what you just read. Create a video or poster to share your five favorite facts from the article!

⇨ Learning Journey: Take a look at the photos in the article again and think about what you just read. Create a video or poster to share your five favorite facts from the article!

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