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12.2: Asio otus: Long-eared Owl

Difficulty Level: At Grade Created by: CK-12
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Common Name

  • Long-eared Owl


Asio otus is called the long-eared owl due to the long tuft of feathers on their forehead. They are often a brownish-gray color, with helping them to blend in with their surroundings.They also have pale patches near the forehead that give the illusion of eyebrows. When they perch, long-eared owls will elongate their wings and compress their feathers.

Female long-eared owls are typically larger and are richer in color than the males, generally ranging from 27 to 40 cm in length and weigh around 260 to 435 g. Males are typically around 35 to 37.5 cm in length and weigh around 260 to 305 g.

The complete taxonomic classification is:

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Aves
  • Order: Strigiformes
  • Family: Strigidae
  • Genus: Asio
  • Species: A. otus


Long-eared owls’ habitats range all throughout the Northern Hemisphere, in areas such as North America, Japan, and Europe. More isolated populations are found near North and East Africa, and the Canary Islands. They are known to inhabit inland, coastal, and desert areas. The long-eared owl can often be found near areas with many tree groves, wetlands surrounded by thickets, grasslands, marshes, and areas near farmlands. During nesting season, long-eared owls will create nests in the old homes of hawks, crows, magpies, and squirrels, or occasionally in natural tree cavities.


Cell Biology

Like all animals, long-eared owls have eukaryotic cells, which are cells that are found in all plants, animals, and fungi (and protists). All eukaryotic cells contain a nucleus and also have many different types of organelles. Organelles basically means “little organs” due to the fact that each organelle plays an important part in the cells function. The organelles of a eukaryotic cell include, aside from the nucleus, the endoplasmic reticulum, which is network of membranes inside the cell; the Golgi bodies, which transport proteins out of the cell and other places throughout the cell; ribosomes, which are particles consisting of RNA and additional proteins, and mitochondria, which is an organelle in which the biochemical processes of cellular respiration and energy production occur. Eukaryotic cells also contain deoxyribonucleic acid, DNA for short. DNA consist of genes with “codes” that serve to make protein for the cells.

The cells of the long-eared owl divide through the process of mitosis and meiosis. Mitosis is when the nucleus of the cell divide is followed by cytokinesis, producing two new cells with the same DNA as the original cell. These cells are said to be genetically identical. This is similar to meiosis, which is the division process of cells in which gametes, which include eggs and sperm cells, are created with half of the chromosomes of the original cell. These chromosomes are compiled of DNA and include “codes” that are responsible for your many traits (ex. hair color, eye color, etc.).

Long-eared owls get their oxygen from the red blood cells in their blood. These red blood cells take oxygen from the lungs and transport it throughout all the organs in the body, including the heart. Like all birds and unlike mammals, the red blood cells of the long-eared owl contains a nucleus. (In mammals, the lack of the nuclei allows higher levels of oxygen to be transported throughout the body.)


The owl species, along with many other birds, are thought to have evolved from theropods, a type of bipedal dinosaurs. Many believe the ancestor of birds was similar to a specific theropod known as Deinonychus. The Deinonychus was a predatory carnivore with many birdlike features such as feathers and wings, along with similar respiratory, circulatory, and digestive systems to modern-day birds. Before the fossils of the Deinonychus were discovered in the 1960s, many scientists did not believe that birds had evolved from dinosaurs. The discovery of these fossils helped to convince the many scientists who had debated the evolution of birds, an idea that had been challenged for close to a century.

Scientists have always pondered on the topic of the evolution of the flight of birds. Several hypotheses and scientific ideas have been presented over many years by various scientists about how and why birds have wings and how these wings evolved. Two of these many theories are listed below.

Theory #1: Some scientists believe that the wings of birds evolved from an ancestor that would leap into the air to either capture prey or avoid predators. Based on this hypothesis, scientists conclude that wing were once modified arms that helped these bird ancestors to leap higher.

Theory #2: Scientists have also introduced the theory that wings evolved from an ancient bird ancestor that lived in trees. Based on this, these scientist believe that the wings were simply modified arms that helped these ancestors to glide from tree to tree with much more speed and ease.

Even though there are many theories on how birds took flight, it is a topic that scientists continue the search for answers, examining fossils of ancient bird ancestors to find out exactly how birds developed wings.


Long-eared owls are the hosts of many internal and external parasites.They mainly hunt animals weighing under 100g. Their key prey includes, but is not limited to, voles and deer mice. Additional prey includes kangaroo rats, pocket gophers, shrews, juvenile rabbits, and other types of rats. They will also occasionally eat small birds, small snakes, and insects. They also relate to hawks, crows, and magpies, as they have been known to settle in the old nests of these animals that have been deserted.

Anatomy and Physiology

Long-eared owl pairs will begin to breed anywhere from the beginning of February to mid-July. Females will lay eggs, generally around 2-10, on 2-day intervals, and will raise 1 brood per season. The eggs have a glossy, smooth texture and generally have a whitish-grayish coloration. These fledglings generally become independent around 11 months, and the average male and female long-eared owl are sexually mature around the age of 1 year old.

The average lifespan for long-eared owls living in the wild is high, around 27.8 years. Long-eared owls have excellent low-light eye site and especially great hearing, both helping them capture concealed prey during nighttime. The flight sounds of long-eared owls are muffled by special wing feathers that allow them to use stealth to sneak up on prey. Like all owls, long-eared owls are unable to chew their food. Instead, they will swallow their smaller prey whole, while tearing larger prey to pieces before consumption. Unlike most birds, owls have no crop. The crop is a loose sac located in the throat that helps most bird species store excess food that will be consumed later. Because owls lack this special feature, all food is passed directly into the digestive system for immediate consumption.

The long-eared owl, along with all birds, have stomachs that consist of two major parts.The first vital organ is the proventriculus. This is part of the anterior glandular stomach that produces gastric acids and digestive enzymes, helping to start the digestive process. The second major part of birds stomachs are the ventriculus or gizzard, which is located in the posterior muscular stomach.The gizzard is the site of chemical digestion and is designed to grind food. It serves a filter to long-eared owls, keeping down indigestible items such as bones, teeth, feathers, and fur.

Before it passes through the rest of the digestive system, muscular contractions will grind down the softer parts of foods. The ground food then passes through the small intestine, where digestive enzymes are released to by the pancreas and liver.

Several hours after eating, the insoluble materials still in the gizzard (bones, feathers, fur, teeth) are compressed into a pellet in the same shape as the gizzard. This pellet is then transferred back up to the proventriculus, where it can remain for up to 10 hours before the regurgitation process begins. Once the regurgitation process is complete, the long-eared owl is allowed to eat once more, due to the fact that the stored pellet partially block the digestive system, which prevents the digestion of new prey before the pellet is ejected. However, if various prey are eaten within a one hour period, the myriad of remains are collected into one large pellet.

Owl pellets differ from the pellets of other birds of prey because they contain more material residue, due to less acidic digestive juices. Owl pellets are released on a regular cycle, regurgitating them once all nutrients have been extracted from the pellet by the digestive system.


Long-eared owls are mainly monogamous, meaning that they will have one mate at a time. Pairs will begin forming in late winter, the males using aerial displays and songs to attract a mate. Females are very protective of the eggs, only leaving the nests for brief periods at night. Long-eared owls arenocturnal, hunting during the night.

The feathers of a long-eared owl can be a key figure on reading its emotions. When long-eared owls are relaxed, their plumage is loose and fluffy. However, as soon as long-eared owls feel threatened, they will make themselves slim looking by pulling their feathers in tightly against the body, and will stick their forehead tufts straight up.




  • Sydney Fortune

Supervising Faculty

  • Amy Huff Shah


  • Museum School, San Diego, California


  • Published prior to review.

Edit History

  • Created: April 5, 2013
  • Version 1.0 submitted to CK-12: June 26, 2013
  • CK-12 edits: in progress


  • Middle School (grades 6-8)

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Date Created:
Jul 08, 2013
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