Biomes

Savanna

Hot grassland with scattered trees
1,334 Animals
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Overview

Understanding This Category

A savanna is a tropical to subtropical biome characterized by a continuous or near-continuous grass layer with a discontinuous canopy of scattered trees and/or shrubs, maintained by interactions among seasonal rainfall, fire, and herbivory. It represents a dynamic intermediate state between closed forests and treeless grasslands, where water limitation and disturbance prevent persistent forest cover.

Savannas are sunny, open lands where grasses cover the ground and trees stand far apart. Strong wet and dry seasons make plants grow in rain and dry out in drought, which helps fires burn. Savannas are stable ecosystems kept patchy by climate, soils, fire, and big plant-eating animals. Many plants and animals have special traits to survive fires and grazing. They occur in Africa, South America, Australia, and parts of Asia, store carbon, hold water, and support livelihoods.

Key Characteristics

Grass-dominated ground layer with scattered trees and/or shrubs (open canopy, variable tree cover).
Strong wet-dry seasonality in precipitation, driving pulses of growth and pronounced dry-season stress.
Frequent fire as a natural and/or human-driven disturbance that limits woody encroachment and maintains openness.
High influence of grazing and browsing by large herbivores, shaping plant communities and nutrient cycling.
Species adapted to drought, fire, and herbivory (e.g., resprouting grasses, thick bark, deciduousness, deep roots).
Mosaic structure and high spatial variability linked to soils, topography, and disturbance history, often forming a stable forest-grassland transition state.
Climate

Climate Conditions

Savanna climates are warm to hot all year (tropical to subtropical) with a strong wet–dry season that controls water, plant growth, and fires. Rain falls mostly in a wet season tied to ITCZ/monsoon shifts, then a long dry season with high water loss, stress, and frequent fires. Grasses dominate; drought- and fire-tolerant trees are scattered.

Temperature

Typically ~5-12°C (9-22°F) difference between mean coolest vs warmest month; larger ranges (up to ~15°C / 27°F) occur in subtropical or more continental savannas.

Average High
~28-34°C (82-93°F) in the warm season; ~24-30°C (75-86°F) in the cooler season (varies by latitude and cloud cover).
Average Low
~16-23°C (61-73°F) in the cooler/drier season; ~20-25°C (68-77°F) in the humid wet season.
Extremes
Heat waves commonly reach ~38-45°C (100-113°F), especially late dry season before rains; occasional cool nights can drop to ~5-10°C (41-50°F) in subtropical/high-elevation savannas, with rare near-freezing events at the margins.

Precipitation

Commonly ~500-1,500 mm/year (20-60 in), with regional variation: drier savannas ~300-700 mm; wetter savannas ~1,000-1,800 mm.

Pattern
Strongly seasonal: ~70-95% of rain falls in a wet season lasting ~3-7 months; the dry season (often 4-8+ months) has little rainfall and prolonged soil moisture deficits.
Humidity
Wet season: moderate to high humidity (often ~60-90% with frequent storms); dry season: low to moderate humidity (often ~20-50%), with dusty air and high evaporative demand.
Seasonality

Savannas have wet and dry seasons. In the wet season grass grows fast, trees leaf out, wetlands fill, and herbivores gather. In the dry season soils dry, grasses become fuel, and fires (from lightning or people) keep the area open. Drought favors deep-rooted, deciduous, thorny, fire-resistant woody plants. Many animals time breeding, migration, or dormancy to follow water and food.

Growing Season

Typically ~90-210 days, aligned mainly with the wet season (and sometimes extending a few weeks after rains end where soils retain moisture). Peak growth is early-to-mid wet season; late dry season growth is minimal except in riparian areas or where groundwater is accessible.

Seasons

Seasonal Changes

Early Wet Season (Green-up)

Typically late spring to early summer; onset varies with latitude and regional monsoon/ITCZ shift (often ~Nov-Jan in southern Africa; ~May-Jun in East Africa/India; ~Nov-Dec in northern Australia).

First sustained rains after the dry season; rapid soil rewetting; warm temperatures; patchy storms; high humidity begins to rise; ephemeral pools and short-lived streams appear; lightning frequency increases.

Explosive grass and forb growth; strong pulse of primary productivity; nutrient mineralization flushes with rewetting; rapid filling of waterholes reduces crowding; tree/shrub leaf-out and flowering in many species; increased insect emergence and decomposition activity.

Large herbivores track fresh, high-protein new grass; grazing pressure concentrates on recently greened areas. Breeding begins for many ungulates and small mammals timed to maximize forage availability for lactation/juvenile growth. Migratory movements start or accelerate toward newly productive plains (where migration exists). Termites and other soil engineers increase activity; mound repair and foraging intensify. Amphibians emerge and breed in temporary pools; water-dependent reptiles become more active. Predators shift hunting to areas of concentrated grazers and birthing grounds.

Peak Wet Season

Mid-summer through late summer; period of most reliable rainfall (often several consecutive months).

Frequent rains; soils often near field capacity; high humidity; warm temperatures; tall grass structure develops; surface water widely available; occasional flooding in lowlands.

Maximum net primary productivity and biomass accumulation; tall, dense grasses reduce visibility and change predator-prey dynamics; rapid plant growth dilutes forage quality over time (fiber increases); high insect biomass supports birds and bats; riparian zones expand; disease vectors (e.g., mosquitoes, tsetse in some regions) may increase.

Herbivores disperse more widely because water is less limiting; some species shift diet toward browse/forbs as grasses mature. Many birds breed; ground-nesters exploit tall grass for cover; insectivores track swarms/flushes. Predation patterns change: ambush predators use tall cover; cursorial hunters may hunt along edges and open patches. Fish colonize seasonal floodplains where present; aquatic food webs boom then set up for later drying. Parasite and pathogen pressures can increase; animals select windy/open microsites or use grooming/wallowing to reduce biting insects.

Late Wet Season (Maturation and Setting Fuel)

Late summer to early autumn; rains become less frequent and more variable before cessation.

Rainfall tapers; intermittent storms; grasses senesce gradually; humidity decreases; waterholes begin to contract; nights may cool slightly in subtropics.

Shift from rapid growth to seed set and senescence; accumulation of continuous fine fuels (drying grass) that will carry fire later; plant reproduction peaks for many grasses/forbs; nutrient allocation to roots and storage organs; increasing spatial heterogeneity as some areas dry first.

Herbivores increasingly target remaining green patches, wetlands, and short-grass areas; mixed feeders increase browsing. Seed-eating birds and rodents peak in abundance/activity as grasses set seed. Some species time weaning/fledging before forage quality declines; others begin dispersal. Predators concentrate near shrinking water sources and movement corridors as animals begin to aggregate.

Early Dry Season (Water Contraction)

Autumn to early winter; immediately after rains stop (length varies widely, often several months total dry season).

Little to no rain; decreasing humidity; grasses cure (dry) rapidly; surface water begins to disappear except in perennial rivers and deeper pans; dust increases; cooler nights in subtropics.

Sharp decline in plant growth; forage quantity remains high but quality drops (higher lignin/fiber); fire risk rises as fuels cure; grazing and trampling intensify around remaining green areas; soil surface begins to harden, increasing runoff when rare storms occur.

Large herbivores shift ranges toward perennial water and higher-quality forage patches (burn scars from prior fires, wetlands, or clay pans that retain moisture). Aggregation around waterholes increases competition and predation risk; dominance hierarchies become more pronounced at water points. Many animals adjust activity to cooler hours; increased nocturnal/crepuscular behavior to reduce heat and water loss. Elephants and other megaherbivores may increase bark-stripping or tree pushing where grasses are poor, influencing woody cover. Birds and mammals use remaining water sources; some species begin local migrations or dispersal.

Late Dry Season (Drought and Fire Season)

Late winter to late spring; the most water-stressed period, often just before the first storms return.

Prolonged drought; very low humidity; hottest temperatures often occur late in the dry season in many savannas; minimal surface water; widespread cured fuels; frequent fires ignited by lightning (late dry) and/or humans; smoke and haze common during burn periods.

Strong resource bottleneck: high mortality risk for water-dependent and young/old individuals; intense grazing pressure on remaining forage; fires remove standing dead grass, recycle nutrients, top-kill woody seedlings/saplings, and create a patch mosaic; post-fire landscapes have improved forage quality but reduced cover; erosion risk increases if heavy rains arrive soon after severe burns.

Concentrated movements to reliable water; longer travel distances between forage and water; increased dehydration stress behaviors (seeking shade, reducing activity). Fire-following behavior: grazers (e.g., wildebeest, zebra, cattle in managed systems) rapidly exploit fresh post-burn regrowth when early rains arrive or when resprouting occurs. Predators hunt along burn edges and near water; scavengers track fire and drought-related carcasses. Burrowing and aestivation increase in some reptiles/amphibians/invertebrates; termites maintain sub-surface activity. Some birds specialize in foraging at active fire fronts (capturing flushed insects/small vertebrates).

Day Length: Savannas occur in tropical to subtropical latitudes, so day length varies modestly compared to temperate zones (near-equatorial ~11.5-12.5 hours year-round; farther subtropical savannas can range roughly ~10-14 hours). Photoperiod is generally a secondary seasonal cue relative to rainfall, but it still contributes to timing of flowering, insect diapause, and some breeding cycles. Ecologically, the key significance is that relatively stable day length means wet-dry rainfall pulses (and associated resource availability and fire regimes) dominate seasonal organization; where day length varies more (subtropics), longer days can amplify dry-season heat and evapotranspiration, intensifying late-dry water stress and shaping migration/aggregation patterns.

Where Found

Global Distribution

Savannas are widespread tropical-subtropical, seasonally dry grasslands with scattered trees and shrubs. They lie between evergreen tropical forests and deserts or steppe, often where wet-dry seasons, frequent fire, and big plant-eating animals keep tree cover open. Largest continuous savannas are in Africa, South America, and northern Australia; others occur in South and Southeast Asia, Central America, and the Caribbean.

~8-12% of Earth's land surface (≈2.3-3.5% of Earth's total surface) of Earth's Surface
~12-18 million km² (global; estimates vary with savanna/woodland definitions) Total Area

Notable Locations

Serengeti-Mara ecosystem (Tanzania/Kenya) Kruger National Park and surrounding savanna landscapes (South Africa/Mozambique) Okavango-Chobe savanna mosaics (Botswana/Namibia) Sahel-Sudan savanna transition zones (West to East Africa) Cerrado biome (Brazil) Llanos (Venezuela/Colombia) Pantanal savanna-wetland mosaics (Brazil/Bolivia/Paraguay) Northern Australian tropical savannas (Kakadu region; Cape York; Kimberley) Cubango-Zambezi savanna woodlands (southern Africa) Pine savannas of Belize and coastal Central America Cuban savannas and pine savannas (Cuba)
Conservation

Conservation Status

Globally, savannas remain widespread but are under high and growing conservation concern due to rapid conversion (especially in the African and South American tropics), altered fire and grazing regimes, and fragmentation; many regions show biodiversity declines even where overall biome area persists.

Declining Trend
Highly variable by region; fastest losses in some tropical savannas (e.g., portions of the South American Cerrado and parts of Africa) can exceed ~0.5-1.5%/year locally, while other regions are closer to stable in area but declining in ecological integrity. Loss Rate

Primary Threats

Agricultural Expansion Habitat Loss Natural System Modification Climate Change Infrastructure Hunting Wildlife Trade Human-Wildlife Conflict Resource Depletion Mining Pollution Invasive Species Disease Urbanization Logging

Protection Efforts

  • Expansion and improved management of protected areas and conservancies (including community conservancies) to maintain large, connected landscapes and migrations
  • Integrated fire management (planned early dry-season burns, patch mosaics, and prevention of late-season high-intensity fires where appropriate)
  • Sustainable rangeland and grazing management (stocking rates, rotational grazing, drought contingency plans) to reduce degradation and erosion
  • Anti-poaching, illegal trade enforcement, and demand-reduction initiatives for key wildlife products
  • Wildlife-friendly infrastructure planning (wildlife corridors, fence modification/removal, road crossing structures, strategic siting of new roads)
  • Community-based natural resource management and benefit-sharing (tourism revenue, grazing agreements, compensation/insurance for conflict)
  • Restoration and reconnection of habitat corridors between protected areas (revegetation, invasive control, fence realignment)
  • Landscape-level land-use planning to reduce conversion pressure in high-biodiversity savannas (e.g., Cerrado safeguards, riparian buffers)
  • One Health approaches to manage livestock-wildlife disease risks (vaccination where appropriate, coordinated surveillance)
Fun Facts

Did You Know?

Fire isn't only destruction in savannas-it can be a "reset button." After a burn, fresh grass regrowth is often extra nutritious, drawing grazers in and jump-starting food webs.

Some savannas occur in climates that could support forest, but frequent fire and heavy grazing keep them open-meaning "more rain" doesn't automatically equal "more trees."

Many savanna plants are built to survive being eaten: grasses can keep their growth points low to the ground, so they can be grazed hard and still regrow quickly.

A lot of savanna biodiversity is hidden underground: many plants store energy in roots or underground stems so they can resprout rapidly after drought, fire, or browsing.

Termites can increase soil fertility and water infiltration; their mounds often act like nutrient-rich "islands," supporting plant communities that differ from the surrounding grassland.

Savannas can store a large fraction of their carbon belowground (roots and soils), so their climate role isn't obvious if you only look at tree cover.

If you lump all the world's savannas together (Africa, South America, Australia, and more), their total area is on the order of ~30 million km²-about the size of the African continent.

A tall termite mound (several meters high) is a skyscraper by termite standards: scaled to human size, an 8 m mound is like building something many hundreds of meters tall relative to your body length.

Savannas often function like a living patchwork quilt: recently burned patches, long-unburned patches, heavily grazed "lawns," and shrubier pockets can sit side-by-side, each favoring different species.

In many savannas, the "forest vs. grassland" boundary is less like a line and more like a tug-of-war-shift fire frequency or grazing pressure, and the balance between trees and grasses can flip.

Savannas collectively cover roughly 20% of Earth's land surface-an enormous swath of the tropics and subtropics shaped by wet-dry seasons, fire, and grazing.

Brazil's Cerrado is widely regarded as the world's most biodiverse savanna, with thousands of plant species (and a high share found nowhere else).

The Serengeti-Mara savanna system supports the largest remaining terrestrial mammal migration on Earth, involving around 1+ million wildebeest plus large numbers of zebra and gazelle.

Many savannas are among the most frequently burned ecosystems on the planet-some landscapes experience fire return intervals of just a few years, and the ecosystem is built to bounce back.

African savannas host some of the greatest remaining concentrations of large wild herbivores and their predators-one reason they're iconic for "big game" diversity and biomass.

Savanna Animals

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