This species was placed in family Dicotylidae by Jones et al. (1992) and in Tayassuidae by Grubb (2005). The appropriate generic name has been debated. It was placed in genus Dicotyles by some authors, the genus Pecari by Grubb (1993, 2005), and the genus Tayassu by Jones et al. (1992). MtDNA data support the recognition of three genera of extant peccaries: Catagonus, Pecari, and Tayassu, with this species in the genus Pecari (Theimer and Keim 1998, Gongora and Moran 2005). DNA studies suggest that P. tajacu may consist of at least two major clades or lineages comprising specimens from North/Central and South America (Gongora et al. 2006, 2011) with structural chromosomal differences (Gongora et al. 2000, Adega et al. 2006). Additional studies are needed to clarify whether intra and/or inter-specific genetic and chromosomal variation is occurring within this species.

Listed as Least Concern as this species is widely distributed and occurs in a variety of habitats, including woodlands, tropical dry and rainforests, savannas, Gran Chaco, and deserts, from the southern USA through to northern Argentina. However, given the continuing rates of habitat destruction and potential for over-hunting of this species, the status of all populations requires monitoring.

The Collared Peccary is widely distributed. It occurs in Arizona, New Mexico, and Texas in the USA, a large part of Mexico and Central America, the entire Amazon basin, the Pacific coastal forest of Colombia, Ecuador and Peru, the llanos and lowland forest of Venezuela, the Guianas and Suriname, all of Brazil where it is increasingly fragmented in the south and east, and the Gran Chaco of Paraguay, Bolivia and northern Argentina where it also occurs in the upper Parana and Paraguay river basins. In Argentina, the species is extinct in the eastern and southern portions of its original distribution. The Argentine population/s of Collared Peccaries in Misiones is isolated from the rest of the country. Some of the larger islands near the mainland in the Caribbean, such as Trinidad and Tobago, also have populations of P. tajacu. However, islands further from the mainland do not currently have peccaries. Their range has recently expanded northward in the southwestern United States (Albert et al. 2004) including into Oklahoma adjacent to Texas (Stangl and Dalquest 1990).

Densities of Collared Peccary differ among habitats. In the south-eastern USA, older reports of densities ranged from 10.9 individuals/km² in the Tucson mountains (Schweinsburg 1969), 7.3 individuals/km² at the King Ranch, Texas and 3.5 individuals/km² at the Welder Wildlife Refuge, Texas, to only 1.1 individuals/km² in a Texas desert. In Venezuela, Collared Peccary density in the llanos was found to be 8 individuals/km², whereas, in gallery forests was 2 individuals/km² (Eisenberg 1980). In the Pantanal of Brazil densities range from 6.6 (forested) to 5.5 (cerrado)  individuals/km² (Desbiez 2007). Densities in tropical forest range from 9 individuals/km² on Barro Colorado Island, Panama (Glanz 1982), to 5 individuals/km² in Manu National Park, Peru (Terborgh et al. 1986). In the Peruvian Amazon, densities range from 3,7 individuals/km² in non-flooded terra firme forest to 1.0 in flooded forest (Fang et al. 2008). In a forest fragment of Atlantic Forest of Brazil, the density found was 5.9 and 6.4 individuals/km² (Cullen 1997, Keuroghlian et al. 2004). In a recent study conducted in the Argentine Chaco, Altrichter and Boaglio (2004) found the Collared Peccary to be more common, widely distributed and present under a wider range of conditions than the other two species of peccaries. Previous studies have shown that Collared Peccaries are less vulnerable than White-lipped Peccaries to habitat fragmentation and hunting pressure, and can maintain healthy populations even in highly degraded areas (Peres 1996, Cullen et al. 2000). The Collared Peccary's smaller herd size and range requirements facilitate its survival in small, disturbed forest remnants (i.e. Atlantic Forest of Brazil), and they have frequently been observed using matrix habitat adjacent to larger forest fragments, e.g. satellite forests and secondary growth (Keuroghlian et al. 2004).

P. tajacu is a highly adaptable species inhabiting a wide variety of habitats from tropical forests to deserts. At the northern fringe of its range, Collared Peccary maintain viable populations in areas where winter night-time temperatures fall below 0° C and light snow cover is occasionally present. The species' tolerance of low seasonal temperatures is exceptional for an animal also living in the tropics (Bodmer and Sowls 1993). The upper limit of its range along the Andean foothills is between 1,000-1,500 m (Grimwood 1969), though they have been found up to 2,000 m asl in Ecudaor (G. Zapata-Rios pers. comm.) and up to 3,000 m asl in the Sierra de las Minas Biosphere Reserve in central-eastern Guatemala (J. Moreira pers. comm.).
Like all peccaries, P. tajacu is a highly social animal, living in herds, which vary from fewer than six to over 30 individuals. Home ranges of groups average approximately 150 ha, but can range from 24 to 800 ha (Sowls 1984). Variation of home range size among different herds in various regions is not unusual. In the Neotropics mean home range estimates of radio-tracked Collared Peccary herds were 102 - 287 ha in the semideciduous Atlantic forest in southeastern Brazil (Keuroghlian et al 2004); 64 – 109 ha in Northwestern Costa Rica (McCoy et al 1990); 460 – 543 ha on the Maraca Island of Brazil (Fragoso 1994); 685 ha in the Chaco of Paraguay (Taber et al 1994); and 157 - 243 ha in the French Guyana (Judas and Henry 1999).
The species' diet varies in accordance with this range of habitats (Beck 2005, 2006). Foods of P. tajacu can include roots, tubers, fruits, seeds, and edible parts of green growing plants, insects, and small animals (Beck 2005, 2005; Desbiez 2007; Keuroghlian and Eaton 2008). Throughout their neotropical range P. tajacu consume fruits from over 128 plant species, and destroy seeds form 79 species (Beck 2006). In tropical forests, diets are dominated by palm fruits (over 25 species, Beck 2005), supplemented with small vertebrates and invertebrates (Bodmer 1989, Beck 2005), whereas in deserts environments their diet is dominated by the cladophylls of prickly pear cactus (Opuntia spp.) (Corn and Warren 1985, Beck 2005). In a heterogeneous environment, the distribution and abundance of resources would be expected to vary among the small, spatially-stable home ranges of Collared Peccary herds. Because each herd uses a unique subset of the available habitat types (McCoy et al 1990, Judas and Henry, 1999, Fragoso,1999; Keuroghlian et al 2004, Neri 2004). The level of frugivory will vary according to local vegetation types or frugivore guild composition (Keuroghlian and Eaton 2008). Frugivory in the Atlantic Forest of Brazil for Collared Peccaries was 78% for both the dry and wet seasons. In the Peruvian Amazon 59 - 66% was composed of fruits (Kiltie 1981, Bodmer 1989); and in the Brazilian Pantanal, frugivory dramatically differed between dry and wet seasons, 17% to 49% respectively (Desbiez 2007).
Habitat and riparian zone use were herd specific for Collared Peccaries in the Atlantic Forest fragment of Brazil, and related to habitat quality and composition where stable home ranges had been established (Neri 2007, Keuroghlian and Eaton in press). Herds are kept together by vocalizations and a strong musk released from the dorsal gland. They deposit scent on tree trunks, rocks and other individuals (Byers 1980). The Collared Peccary has a diurnal/crepuscular activity pattern, typically feeding in early hours of the night but varying seasonally. They commonly rest in small groups of three to four individuals and often seek shelter in burrows, caves and under logs. Collared Peccaries frequently wallow in mud or dust and rarely spend time auto-grooming (Sowls 1984). Keuroghlian et al 2004 observed that subgrouping of herds occurred on a different spatial and temporal scale than the subherding of White-lipped Peccaries. Usually, a herd would be united early in the morning and again in late afternoon, but would split into groups of 1 to 3 individuals during the day. These subgroups appeared to forage separately and were from 30 to 250 m apart. Sightings of lone Collared Peccaries or groups of 2 to 3 individuals have frequently been reported from sites in both the Neotropics and the southwestern United States (Kiltie and Terborgh, 1983; Robinson and Eisenberg, 1985; Sowls, 1997; Castellanos, 1983; Oldenburg et al. 1985; Bissonette, 1976; Green et al. 1984). Collared Peccaries appeared to travel more in the early morning and late afternoon, when the full herd was together. During midday, subherds would usually remain in a relatively restricted area foraging. They also spent a good part of late morning and early afternoon resting in cavities excavated at the bases of large trees, next to fallen trunks, or in other cool locations (Taber et al. 1994, Keuroghlian et al. 2004).
Births have been recorded year-round, though in the southern USA there is a birth peak during the summer rainy season. In the Amazon, the Collared Peccary female is considered to be aseasonally polyoestrous (Mayor et al. 2006), with an oestrous cycle length of 27.8 ± 1.5 days (Mauget et al. 1997), a mean gestation period of 138 days (Mayor et al. 2005), a pregnancy rate of 42.5% (Mayor et al. 2010) and a litter size of 1.7 – 1.9 foetuses or newborns (Gottdenker and Bodmer 1998, Mayor et al. 2006). Reproductive production of the species in the wild was estimated at 1.12 births/year and 1.98 piglets per pregnant female (Mayor et al. 2010). Collared Peccary females presented a mean ovulation rate of 2.25 ± 0.58 CLs, a litter size of 1.77 ± 0.48 embryos or foetuses and a reproductive wastage of 0.45 ± 0.65 (21.3%) oocytes or embryos per pregnant female female (Mayor et al. 2010). Among 163 piglets, 78 were females and 85 were males. The young are highly precocial at birth, following their mothers within an hour of parturition and stopping to suckle at frequent intervals. In one case infants were observed to spend up to 24% of their time suckling (Sowls 1966). Weaning occurs at approximately 6 weeks (Sowls 1984).

The two major threats to the survival of Collared Peccary are over-hunting for their meat and hides and excessive destruction of its natural habitats. These factors have already resulted in the extensive fragmentation of peccary populations and its extirpation over large parts of its former range (Bodmer and Sowls 1993). The Collared Peccary (Pecari tajacu) and White-lipped Peccary (Tayassu pecari) are important resources for subsistence hunters of the Peruvian Amazon (Bodmer et al. 2004a). In Peru, subsistence hunting of peccaries is legally defined as the use of peccary meat for household consumption or the sale of peccary meat in settlements of fewer than 3,000 inhabitants. Rural inhabitants hunt peccaries mainly for their meat, which have an economic value of approximately $23 for a Collared Peccary and $30 for a white-lipped peccary either as subsistence food or through local sale (Bodmer et al. 2004b). Peccary pelts are sold as a by-product and have an economic value to hunters of approximately $5 for a Collared Peccary pelt and $3 for a White-lipped Peccary pelt (Bodmer and Pezo 2001, Fang 2003). Approximately 51,419 Collared Peccary pelts and 20,522 White-lipped Peccary pelts are legally exported with CITES permits every year from Peru under a quota system imposed by the Peruvian government (INRENA 2004). The pelts are tanned in Peru and primarily sold to the European leather industry for the manufacture of high quality gloves and shoes. However, it is unclear if this trade increases the hunting pressure to meet the quotas. Furthermore, how many individuals have to be killed to obtain pelts that meet the quality standards of international trade (assuming that a given number of pelt are rejected because of scars, parasite marks i.e. bot flies, and bullet holes). In addition, considering that peccary glove can sell for as much as $285, a $5 reward for a Collared Peccary pelt does not qualify as a fare trade. On the other hand, increasing the dollar value would certainly further increase the hunting pressure.

It is hunted heavily for food, and its hides are traded internationally.

Collared Peccaries occur in a large number of national parks and other reserves throughout their extensive range in the Americas. In many of these areas populations are relatively secure, although poaching and inefficient protection are common and may nullify the nominal protection afforded by the designation of protected sites (Bodmer and Sowls 1993). Conservation measures specific to Collared Peccaries include national wildlife protection legislatures, which vary from country to country, and the inclusion in 1986 of this and other peccary species on the Appendices of CITES. The Collared Peccary was originally placed on Appendix III of CITES and in 1986 it was elevated to Appendix II (except the populations of Mexico and the United States of America, which are not included in the Appendices). Specific management regulations appertaining to hunting and movement of peccary products exist for all countries within the geographical range of P. tajacu. In the USA, for example, the species is managed as a game animal outside national parks and reserves, and may be hunted with permits under a quota system operated by state authorities. In Brazil there is a total ban on all hunting of peccaries by non-indigenous people, though this is largely unenforced in many states. Subsistence hunting is permitted in Colombia and Venezuela, but these countries prohibit the movement of peccary products, whilst in other countries, such as Peru, subsistence hunters are allowed to trade peccary products under management laws. However, in these and many Central and South American countries, rural people are often unaware of wildlife management regulations or these are flouted, sometimes quite openly, owing to the common lack of resources and trained personnel for the enforcement of protective legislation.