Once a species becomes listed as endangered or threatened under the Endangered Species Act it is afforded the following protections:

• Import, export, and interstate or foreign sales are prohibited without a special permit.

• Taking is illegal—Taking is killing, harming, harassing, pursuing, or removing the species from the wild.
• Federal agencies must conduct their activities in such a way as to conserve the species.
• Federal agencies that manage lands and/or waters must consult with the U.S. Fish and Wildlife Service or National Marine Fisheries Service regarding conserving listed species in those habitats. Any activities funded or authorized by those federal agencies or carried out on lands or waters managed by them can not jeopardize the survival of the listed species.

Civil and criminal penalties can be levied for violations of these provisions. However, exemptions are granted for native peoples of Alaska that rely on certain endangered or threatened animals for food or other products needed for subsistence. In addition, section 4(d) of the Endangered Species Act allows the Fish and Wildlife Service to grant other exemptions from the "taking" rule for threatened species. For example, the gray wolf in Minnesota falls under a 4(d) rule that allows certain government agents to kill wolves that prey on domestic animals. The rule was created to prevent private citizens from performing wolf control to protect livestock. A 4(d) rule is commonly referred to as a "special rule" under the ESA.

Endangered species have different needs and require different conservation measures. Some fish are endangered only because of a history of overfishing. Halting or reducing fishing is sufficient for population recovery. In most cases, however, more active forms of intervention are necessary. The single most important conservation measure for many threatened and endangered species is habitat conservation or restoration. For some species, captive breeding followed by reintroduction into the wild may help increase numbers. In all cases, knowledge of the natural history of endangered species is essential to acquiring a better understanding of species' needs, as well as to the development of measures that will aid in conservation.

Under the Endangered Species Act the FWS or NMFS must decide whether critical habitat should be designated for a listed species. Critical habitat is specific geographical areas of land, water, and/or air space that contain features essential for the conservation of a listed species and that may require special management and protection. For example, these could be areas used for breeding, resting, and feeding. If the agencies decide that critical habitat should be designated, a proposal notice is published in the Federal Register for public comment. If it is decided that critical habitat is needed, then the final boundaries are published in the Federal Register.

The role of critical habitat is often misunderstood by the public. Critical habitat designation does not set up a refuge or sanctuary for a species in which no development can take place. It can provide additional protection for a specific geographical area that might not occur without the designation. For example, if the FWS determines that an area not currently occupied by a species is needed for species recovery and designates that area as critical habitat, any federal actions involving that area have to avoid adverse modifications. Critical habitat designation has no regulatory impact on private landowners unless they wish to take actions on their land that involve federal funding or permits.

The original ESA did not provide a time limit for the setting of critical habitat. In 1978 the law was amended to require that critical habitat be designated at the same time a species is listed. However, the designation is only required "when prudent." For example, the Fish and Wildlife Service or National Marine Fisheries Service can refuse to designate critical habitat for a species if doing so would publicize the specific locations of organisms known to be targets for illegal hunting or collection. Historically the agencies have broadly used the "when prudent" clause to justify not setting critical habitat for many listed species. This has been a very contentious issue between the government and conservation groups.

As of February 23, 2006, critical habitat had been designated for 473 species. This represents just over onethird of all U.S. species listed under the ESA. Plants make up more than half of the listed species for which critical habitat has been designated.

For a small number of species, primarily mammals, birds, fish, and aquatic invertebrates, recovery efforts include the introduction of individuals into new areas. Typically this is accomplished by moving a small group of imperiled animals from an established area to one or more other locations within their historical range of distribution.

Experimental populations of a species are not subject to the same rigorous protections under the Endangered Species Act as other members of the species. Experimental populations can be considered threatened, even if the rest of the species is listed as endangered. In addition, the FWS can designate an experimental population as essential or nonessential. A nonessential designation indicates that the survival of this population is not believed essential to the survival of the species as a whole. A nonessential experimental population (EXPN or XN) is treated under the law as if it is proposed for listing, not already listed. This results in less protection under the ESA.

As of February 2006 there were thirty-seven experimental populations listed under the ESA for thirty-three TABLE 2.5 Recovery potential priority ranking system "Table 2. Fish and Wildlife Service's Recovery Priority Ranking Schedule," in Endangered Species: Fish and Wildlife Service Generally Focuses Recovery Funding on High-Priority Species, But Needs to Periodically Assess Its Funding Decisions, U.S. Government Accountability Office, April 2005, http://www.gao.gov/new.items/d05211.pdf (accessed February 25, 2006)separate species. Clams and snails comprise more than half the animals represented. Notable experimental populations for mammals include the grizzly bear and gray wolf. Both have been reintroduced into portions of western states.

The ESA requires that a recovery plan be developed and implemented for every listed species unless "such a plan will not promote the conservation of the species." The Fish and Wildlife Service and National Marine Fisheries Service are directed to give priority to those species that are most likely to benefit from having a plan in place. The recovery potential of species is ranked from 1 to 18 as shown in Table 2.5. Low rankings indicate a greater likelihood that the species can be recovered. Priority is based on the degree of threat, potential for recovery, and taxonomy (genetic distinctiveness). In addition, rankings can be appended with the letter "c" when species recovery is in conflict with economic activities. Species with a "c" designation have higher priority than other species within the same numerical ranking.

Each recovery plan must include the following three elements:

• Site-specific management actions to achieve the plan's goals
• Objective and measurable criteria for determining when a species is recovered
• Estimates of the amount of time and money that will be required to achieve recovery

Recovery plans include precisely defined milestones for recovery achievement. For example, recovery may be considered accomplished when a certain number of individuals is reached and specifically named threats are eliminated.

Notices regarding proposed new or revised recovery plans must be placed in the Federal Register so that public comment can be obtained and considered before a plan is finalized.

When the original ESA was passed it included exceptions that allowed "taking" of listed species only for scientific research or other conservation activities authorized by the act. In 1982 Congress added a provision in Section 10 of the ESA that allows "incidental take" of listed species of wildlife by nonfederal entities. Incidental take is defined as take that is incidental to, but not the purpose of, an otherwise lawful activity. Incidental taking cannot appreciably reduce the likelihood of the survival and recovery of listed species in the wild. The incidental take provision was added to allow private landowners some freedom to develop their land even if it provides habitat to listed species.

In order to obtain an incidental take permit, an applicant has to prepare a Habitat Conservation Plan (HCP). An HCP describes the impacts likely to result from the taking of the species and the measures the applicant will take to minimize and mitigate the impacts. HCPs are generally partnerships drawn up by people at the local level, working with officials from the Fish and Wildlife Service or the National Marine Fisheries Service. The plans frequently represent compromises between developers and environmentalists.

Included in the agreement is a "no surprise" provision that assures landowners or developers that the overall cost of species protection measures will be limited to what has been agreed to under the Habitat Conservation Plan. In return, landowners make a long-term commitment to conservation as negotiated in the HCP. Many HCPs include the preservation of significant areas of habitat for endangered species.

Although the HCP program was implemented in 1982, it was little used before 1992, with only fourteen permits issued in that time period. As of February 28, 2006, there were 446 HCPs in place covering dozens of species. More than half of the Habitat Conservation Plans were issued in FWS regions for the southwest and southeast states. By far, the animal with the most plans issued is the Houston toad with more than 200 HCPs in place. Information about HCPs is available in a database at the FWS Web site (http://ecos.fws.gov/conserv_plans/public.jsp). The database includes the locations covered by the plans as well as information on the applicants and the listed and unlisted species involved.