In comparison to other parts of Nepal, the Park has a comparatively low number of mammals, probably due in part to the geologically recent origin of the range. Larger mammals include northern plains grey langur Semnopithecus entellus, jackal Canis aureus, grey wolf Canis lupus (but not seen since 1980), Himalayan black bear Ursus thibetanus (VU), red panda Ailurus fulgens (VU), yellow-throated marten Martes flavigula, Siberian weasel Mustela sibirica, snow leopard Panthera uncia (EN), masked palm civet Paguma larvata, sambar Rusa unicolor (VU), Himalayan musk deer Moschus leucogaster (EN), southern red muntjac Muntiacus muntjak, Sumatran serow Capricornis sumatraensis (VU), Himalayan tahr Hemitragus jemlahicus (300) and Himalayan goral Naemorhedus goral (Jefferies & Clarbrough,1986; Lovari,1990). Results from recent surveys suggest that populations of both tahr and musk deer have increased substantially since the Park was gazetted and has led to a recovery of the snow leopard population. Smaller mammals include web-footed water shrew Nectogale elegans, Himalayan water shrew Chimarrogale himalayica, short-tailed mole Talpa micrura, woolly hare Lepus oiostolus, bobak marmot Marmota bobak, Royle's pika Ochotona roylei , rat Rattus sp. and house mouse Mus musculus (Garratt,1981). The Park is important for a number of high altitude breeding species, such as blood pheasant Ithaginis cruentus, robin accentor Prunella rubeculoides, whitethroated redstart Phoenicurus schisticeps, grandala Grandala coelicolor and several rosefinches. The Park's small lakes, especially those at Gokyo, are staging points for migrants and at least 19 water bird species have been recorded including ferruginous duck Aythya nyroca, and demoiselle crane Grus virgo, also wood snipe Gallinago nemoricola (VU) (Inskipp, 1989; Scott, 1989). Bar-headed geese Anser indicus fly over the mountain, and the yellow-billed chough Pyrrhocorax graculus has been seen as high as the South Col (7,920m) (Hunt, 1953). A total of six amphibians and seven reptiles occur or probably occur in the park. Documentation of the invertebrate fauna is limited, though Euophrys omnisuperstes, a minute black jumping spider has been found in crevices at 6,700 metres (Wanless, 1975), and 30 butterfly species have been seen, among them the orange and silver mountain hopper Carterocephalus avanti , which is not recorded elsewhere in Nepal, and the rare red apollo Parnassius epaphus (Jefferies & Clarbrough,1986).
Six vegetation zones as described for the Nepal Himalaya by Dobremez (1975) exist in the Park: lower subalpine, above 3,000m, with forests of blue pine Pinus wallichiana, east Himalayan fir Abies spectabilis and drooping juniper Juniperus recurva; upper subalpine above 3,600m, with birch rhododendron forest of Himalayan birch Betula utilis, Rhododendron campanulatum and R. campylocarpum; lower alpine, above the timber-line at 3,800-4,000m, with scrub of Juniperus species, Rhododendron anthopogon and R. lepidotum; upper alpine, above 4,500m, with grassland and dwarf shrubs; and sub-nival zone with cushion plants from about 5,750-6,000m. Above this conditions are arctic. In the upper montane zone the oak Quercus semecarpifolia used to be the dominant species but former stands of this species and Abies spectabilis have been colonised by pines. Rhododendron arboreum, R. triflorum, and Himalayan yew Taxus wallichiana are associated with pine at lower altitudes with the shrubs Pieris formosa, Cotoneaster microphyllus and R. lepidotum. The vines Virginia creeper Parthenocissus himalayana and Clematis montana are also common. Other low altitude trees include the maple Acer campbellii and whitebeam Sorbus cuspidata. Abies spectabilis occupies medium to good sites above 3,000m and forms stands with Rhododendron campanulatum or Betula utilis.
Towards the tree line, R. campanulatum is generally dominant. Black juniper Juniperus indica occurs above 4,000m, where conditions are drier, along with dwarf rhododendrons and cotoneasters, shrubby cinquefoil Potentilla fruticosa var.rigida, Sikkim willow Salix sikkimensis and Cassiope fastigiata. In association with these shrubs is a variety of herbs: Gentiana prolata, G. stellata, Leontopodium stracheyi , Codonopsis thalictrifolia, Thalictrum chelidonii , the lilies Lilium nepalense and
Notholirion macrophyllum, Fritillaria cirrhosa and primroses, Primula denticulata, P. atrodentata, P. wollastonii and P. sikkimensis. The shrub layer diminishes as conditions cool, and above 5,000m R. nivale is the sole rhododendron. Other dwarf shrubs in the dry valley uplands include buckthorn Hippophae tibetana, horsetail Ephedra gerardiana, black juniper and cinquefoil Potentilla fruticosa. Associated herbs are gentians, Gentiana ornata and G. algida var.przewalskii , edelweiss Leontopodium jacotianum and Himalayan blue poppy Meconopsis horridula. Above this and up to the permanent snow line at about 5,750m, plant life is restricted to lichens, mosses, dwarf grasses, sedges and alpines such as Arenaria polytrichoides and Tanacetum gossypinum.