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A nocturnal, burrowing, insectivorous, piglike mammal (Orycteropus afer) in the order Tubulidentata. The mammalian order Tubulidentata contains a single family, Orycteropodidae, and a single extant aardvark species, Orycteropus afer (Fig. 1).…

A discipline within the field of animal behavior that focuses on the reception and use of signals. Animal communication could well include all of animal behavior because a liberal definition of the term signal could encompass all stimuli perceived…

The group of primates most closely related to humans. The primates included in the ape group are the African great apes, the gorillas (Fig. 1) and chimpanzees; the Asian great apes, the orangutans; and the lesser apes from Asia, the gibbons. Humans…

A taxonomic order of insects comprising the cockroaches and termites. The order Blattodea, also referred to as Blattaria, contains at least 4500 species of cockroaches (Fig. 1) and 3000 species of termites. Previously, termites were assigned to a…

The common name used to describe any member of the carnivoran mammalian family Felidae. Members of the family Felidae (order Carnivora, class Mammalia) are known as cats. Typically, in common usage, the term is restricted to the domestic cat and…

Neonicotinoid insecticides are the most used insecticide worldwide and have been linked to the decline of pollinator insects. In 2018, the European Union banned the outdoor use of three neonicotinoid insecticides: clothianidin, imidacloprid, and…

An aquatic mammalian order comprising approximately 90 living species of whales, dolphins, and porpoises and their fossil relatives. Like all other mammals, members of the order Cetacea (cetaceans) nurse their young with milk produced by the mother,…

Colony collapse disorder (CCD) is a baffling detrimental condition in colonies of honeybees (Apis mellifera). It is characterized by a rapid loss of the adult bee population, with an absence of dead bees in and around affected colonies. No single…

An order of sea urchins (class Echinoidea) possessing an aulodont Aristotle's lantern (jaw apparatus) with unkeeled teeth that are U-shaped in cross section, and with the apophyses not meeting at the top of the lantern. In Diadematoida, the…

Members of the carnivorous mammalian family Canidae. All breeds of domestic dogs (Fig. 1), the wild dogs, and related species belong to the family Canidae. Despite the various breeds of domestic dogs that are known, the scientific name for all types…

Conservationists have determined that the Bornean orangutan (Pongo pygmaeus) is disappearing much more rapidly than previously thought. Since 1999, the total number of Bornean orangutans declined by at least 148,000 individuals. The chief culprits…

The warming temperatures attributed to global climate change are making it more difficult for sea turtle populations to survive. As a result of the unusual developmental processes found in many reptiles, including some species of turtles, the sex of…

A taxonomic domain consisting of the vast array of living and fossil organisms with complex cells in which the genetic material is organized into chromosomes [linear pieces of deoxyribonucleic acid (DNA) bound with histone proteins and visible as…

The prevalence of diseases caused by ticks, mosquitoes, and fleas that feed on the blood of humans has increased dramatically. Over a 13-year span (the years 2004 through 2016), the incidence of tick-, mosquito-, and flea-borne diseases in humans…

The evolutionary transition of certain dinosaurs into modern birds has long been an active area of paleontological research. Because the members of the class Aves are living representatives of theropod dinosaurs, paleontologists have sought fossil…

A predatory, cosmopolitan cetacean mammal, Orcinus orca, found typically in cold ocean waters. Killer whales (Orcinus orca) [Fig. 1] are top (apex) predators in the marine ecosystem, with no natural enemies other than humans. These carnivorous…

In the fall of 2014 and early winter of 2015, an estimated 250,000 to 500,000 seabirds known as Cassin's auklets (Ptychoramphus aleuticus) died along the Pacific Coast from California to British Columbia, Canada. Researchers have now reported the…

The names associated with a great number of species of mammals in a number of different families of the order Rodentia. The rodents constitute the largest order (Rodentia) of mammals, and they include approximately 2300 species, or about 42% of the…

Neonicotinoids (also termed neonics) comprise a class of insecticides and pesticides that chemically resemble nicotine. They are the most widely used insecticides in the world and are deployed by plant and crop farmers because these chemical…

The Northern white rhinoceros (Ceratotherium simum cottoni)—one of two white rhino subspecies—is functionally extinct. Officially, this subspecies is classified by the International Union for Conservation of Nature and Natural Resources (IUCN) as…

A newly identified reptilian fossil has pushed back the phylogenetic (evolutionary) family tree of Squamata [the dominant order of living reptiles, comprising lizards, snakes, and amphisbaenians (mostly limbless lizards that resemble worms)] by 75…

The Iberian lynx (Lynx pardinus; also known as the Spanish lynx), which inhabits the shrublands of southwestern Spain and Portugal, was on the verge of extinction at the beginning of the twenty-first century. At that time, this wild cat species was…

The cultivation and harvesting (aquaculture) of salmon species. Salmon is the common name assigned to various fish belonging to the genera Oncorhynchus and Salmo (Fig. 1) in the order Salmoniformes. These relatively large, predatory fish live in…

A small monotypic order of flightless, marine swimming birds, comprising the penguins, found predominantly in the colder southern oceans. Penguins (Fig. 1) constitute the order Sphenisciformes in the class Aves. Depending on the classification…

A social insect, often destructive to wooden structures, assigned to the order Blattodea. Termites (Fig. 1) have the general characteristics and stages of other exopterygote insects [that is, insects having a simple (incomplete) metamorphosis…

The apes are a branch of Old World primates, distinguished from monkeys by their mode of locomotion (arm swinging, rather than quadrupedal walking). It has long been known that humans are more closely related to apes than to other primates. However,…

The management and maintenance of colonies of honeybees for human purposes. Beekeeping is an ancient art. Although the commonly known honeybee species (Fig. 1) is native to Europe and Africa, humans have transported them to other continents. The…

An order of extinct 10-armed cephalopod mollusks with an internal shell. The order Belemnitida belongs to the subclass Coleoidea in the class Cephalopoda (phylum Mollusca). Constituent members, which are all extinct, are known as belemnites (Fig.…

Terrestrial and aquatic animals that are capable of excavating holes in the ground for protection from adverse environmental conditions, as well as for storing food. Burrowing animals are uniquely adapted species, having the capacity to dig burrows…

The behavior of wild chimpanzees (Pan troglodytes) [Fig. 1] is fascinating because of its similarity to human behavior. These behavioral similarities are due in part to the close evolutionary relationship between chimpanzees and humans. Behavioral…

A phylum of ciliated protozoans. The members of the phylum Ciliophora (also Ciliata), known commonly as ciliates (Fig. 1), constitute a fairly homogeneous group of highly differentiated, unicellular organisms. They are distinguished principally by…

Coral reefs proliferate in ocean waters that are oligotrophic, that is, extremely poor in nutrients. This paradox, first noted by Charles Darwin when he passed through Tahiti in 1842, was difficult to comprehend until symbiotic relationships between…

There are four species of African great apes living today, two chimpanzees [common chimpanzee (Fig. 1) and bonobo (pygmy chimpanzee)] and two gorillas (western gorilla and eastern gorilla), with degrees of subspecies differentiation within them.…

In 2016, animal researchers and geneticists concluded that the giraffe (genus Giraffa), once thought to consist of a single extant species (Giraffa camelopardalis), comprises four distinct species: the northern giraffe (Giraffa camelopardalis),…

Millions of species make up the extraordinary variety of organisms on Earth. The evolutionary variety is displayed in miniature by several groups of animals and plants that have diversified rapidly. Among these is a group of 18 species called…

A former order or subclass of ciliated protozoa. The protozoan order or subclass known as Holotrichia (also spelled Holotricha) is no longer a valid taxon. However, the word holotrich is still used as a descriptive term to identify protozoa with a…

Survival prospects for the honeybee (Apis mellifera) look increasingly promising as entomologists and beekeepers have reported a dramatic increase in the population numbers of these essential insects in North America and Europe. Honeybees, which are…

An order of ciliated protozoans. The order Hymenostomatida belongs to the protozoan class Oligohymenophorea (phylum Ciliophora) and contains many species that often are of small size and fairly uniform ciliation. Primarily, the members of the order…

Through study of the fossil record, paleontologists can frequently identify when an ancient species or taxon (a grouping of related organisms) first emerged in evolutionary history. (Paleontologists often prefer the term taxon over species because…

Molting (shedding or ecdysis) of the outer cuticular layer of the body is a process vital to arthropods, including insects and crustaceans. This profound endocrinological and physiological process has undoubtedly helped ensure the evolutionary…

A new species of orangutan has been identified in the Batang Toru forest ecosystem in northern Sumatra, Indonesia. Genetic and morphological evidence, as well as behavioral data, have confirmed that the Tapanuli orangutan (Pongo tapanuliensis) is…

A genus of unicellular shelled foraminifers (family Nummulitidae). Members of the genus Nummulites (termed nummulites) are single-celled protoctists (protozoa) of the Foraminifera taxon (which is typically regarded as a phylum or subphylum,…

An order of coleoid cephalopods, characterized by eight appendages that encircle the mouth, a saclike body, and an internal shell that is much modified or reduced from that of its ancestors. The origins of the order Octopoda (subclass Coleoidea,…

A suborder of trilobites (a class of extinct arthropods) and a diverse clade consisting of roughly 100 distinct species. The trilobites constituting the suborder Olenellina belong to the order Redlichiida in the class Trilobita. These extinct…

An order of gastropods belonging to the Opisthobranchia and consisting of the sap-sucking sea slugs. The order Sacoglossa (alternatively called Ascoglossa) belongs to the informal group Opisthobranchia (clade Heterobranchia, class Gastropoda,…

Although the survival of the snow leopard (Panthera uncia; formerly, Uncia uncia), also known as the ounce, is precarious, the International Union for Conservation of Nature and Natural Resources (IUCN) has assigned an upgraded…

Infectious viral diseases spread through the bite of blood-feeding ticks. Tick-borne diseases have emerged as a public health concern, especially in Europe, Asia, and North America. They occur in pigs, sheep, goats, and humans and are caused by…

A class of extinct Paleozoic arthropods, occurring in marine rocks of Early Cambrian through Late Permian age. The members of the extinct arthropod class Trilobita are commonly known as trilobites (Fig. 1). About 5000 described genera and 17,000…

Predators actively hunt, kill, and consume their prey for the sake of nutrition. Although the stakes are high for both parties involved, they are more important for the prey item. If the prey loses in the interaction, it loses its life, whereas the…

A large, rabbit-sized rodent, belonging to the family Dasyproctidae and inhabiting South America and Central America, which is well adapted for speed because of its elongated hind legs. The agouti is a large rodent that resembles the rabbit or hare…

Vicugna pacos, a member of the camel family (Camelidae), which has been domesticated for more than 2000 years and is economically important for its long, fine wool. The alpaca (Vicugna pacos; formerly, Lama pacos) [see illustration] belongs to the…

Any of several living mammals in the suborder Vermilingua in the order Pilosa that feed on ants and termites. The common name of anteater is assigned to four species of living mammals classified in the suborder Vermilingua in the order Pilosa…

A heavily armored mammal in the order Cingulata. The order Cingulata (formerly Edentata or Xenarthra) comprises the armadillos, which are divided into two extant families: Chlamyphoridae and Dasypodidae. These creatures are characterized by bony…

The only surviving subclass of the echinoderm class Crinoidea. The Articulata include all living members of the echinoderm class Crinoidea and are generally regarded as the post-Paleozoic crinoids. Crinoids are exclusively marine organisms, as are…

The common name for a number of carnivorous mammals in the family Mustelidae. Badgers are members of the carnivorous mammalian family Mustelidae, which also contains the weasels, otters, minks, ferrets, martens, sables, fishers, and wolverines.…

The dance language of honeybees (Apis mellifera) is a unique form of animal behavior and communication that was discovered by the zoologist Karl von Frisch (1886–1982) in the 1920s, which he continued to study through the 1960s and for which he was…

The name for two species (genus Bison) of the cattle family Bovidae in the mammalian order Artiodactyla found in North America and Europe. The North American bison (Bison bison; see illustration) is often called buffalo, but should not be confused…

The name for several species of small ruminant mammals, also called mouse deer, which constitute the family Tragulidae in the order Artiodactyla. Chevrotains, often known as mouse deer (also spelled mouse-deer), belong to the family Tragulidae in…

A large homopteran insect of the superfamily Cicadoidea generally having long transparent wings and with the male typically producing a loud, droning noise. Cicadas are a large and diverse group of insects belonging to the superfamily Cicadoidea…

Any of the species of carnivorous mammals assigned to the genera Nasua and Nasuella in the raccoon family Procyonidae. The most current classification recognizes four species of coatis. The common, South American, or ring-tailed coati (Nasua nasua)…

A detrimental condition in honeybee colonies characterized by a rapid loss of the adult bee population, with an absence of dead bees in and around affected colonies. Colony collapse disorder (CCD) first came to light in the fall of 2006. Since that…

A large, tawny brown wild cat, Puma concolor (family Felidae), once widespread over most of the Americas; also known as catamount, mountain lion, painter, and puma. The cougar (Puma concolor; see illustration) is a carnivorous member of the family…

An order of bryozoans in the class Stenolaemata. Members of the order Cyclostomatida (previously termed Cyclostomata or Tubuliporata) belong to the class Stenolaemata in the phylum Bryozoa. Known commonly as cyclostomes (although not to be confused…

In 2016, the eastern lowland gorilla (Gorilla beringei graueri), also known as Grauer's gorilla, was identified as critically endangered because of the precipitous drop in its population by more than 77% over the past few decades. The critically…

The former name of an order that included the Xenarthra (sloths, anteaters, and armadillos), Pholidota (pangolins), and Tubulidentata (aardvarks). The former order Edentata was so named because of the apparent lack of some or all teeth of its…

One of two extant orders of brittle stars, comprising the basket stars and snake stars, in the class Ophiuroidea (phylum Echinodermata). The order Euryalida currently includes approximately 190 valid species worldwide, which represents a little…

The name given to any of three carnivorous mammals in the genus Mustela (family Mustelidae); also known as the polecat. There are three species of ferrets, also termed polecats, belonging to the genus Mustela in the family Mustelidae of the order…

A medium-sized, weasel-like, carnivorous mammal (Martes pennanti or Pekania pennanti) classified in the family Mustelidae. Fishers (Martes pennanti or Pekania pennanti) belong to the family Mustelidae (order Carnivora), which also includes weasels,…

A disease caused by the protozoan parasite Giardia lamblia, characterized by chronic diarrhea that usually lasts one or more weeks. The presence of the protozoan parasite Giardia lamblia (also known as Giardia intestinalis and Giardia duodenalis)…

An artiodactyl member of the genus Giraffa in the mammalian family Giraffidae. The giraffe (see illustration) is the only extant member of the genus Giraffa (family Giraffidae, class Mammalia). Once thought to consist of a single extant species…

The extinct members of the mammalian subfamily Glyptodontinae are known as glyptodonts. These prehistoric creatures resembled gigantic, heavily armored armadillos, and they possessed a protective shell of bony plates that measured up to 1.5 meters…

A superclass of the subphylum Vertebrata consisting of animals that possess jaws. The superclass Gnathostomata comprises the jawed vertebrates (subphylum Vertebrata, phylum Chordata). In other words, gnathostomes are animals with jaws, involving a…

The common name for members of the insectivorous mammalian family Erinaceidae (order Eulipotyphla) generally characterized by spines on their back and sides. Hedgehogs belong to the mammalian family Erinaceidae in the order Eulipotyphla (formerly,…

One of the evolutionary lineages of gastropods (class Gastropoda), comprising a very heterogeneous group of snails with forms that resemble typical marine snails with external spiraled shells such as sundial shells (family Architectonicidae), sea…

An African carnivore belonging to the family Hyaenidae. The family Hyaenidae (order Carnivora) comprises three species of hyenas (also spelled hyaenas): one species in the genus Crocuta (see illustration) and two species in the genus Hyaena. In…

An obsolete order of placental insectivorous mammals, now mostly reassigned to the order Eulipotyphla, including the shrews, moles, hedgehogs, and solenodons. The order Insectivora was formerly thought by taxonomists to be a basal placental order,…

The common name for members of the agnathans. The superclass Agnatha (subphylum Vertebrata, phylum Chordata) comprises the jawless vertebrates (agnathans). Members include the cyclostomes (modern lampreys and hagfishes), as well as extinct armored…

Lama glama, a member of the camel family (Camelidae) found only in South America. The llama (see illustration) is an artiodactyl, or even-toed ungulate, belonging to the mammalian family Camelidae. It has two toes on each foot. The llama is a…

An order of small insectivorous mammals, commonly known as the elephant shrews, containing the single family Macroscelididae. The elephant shrews, also called sengis, constitute the Macroscelididae, the sole family of the order Macroscelidea. They…