Nyala Woodland Vigilance Lab (2D)

Herd Parameters

Herd size 16

Woodland density 50%

Denser thicket hides the herd from a stalking leopard, but also shortens how far any individual can see it coming.

Bull ratio 30%

Vigilance coordination 1.0×

How efficiently the herd shares scanning duty instead of scanning redundantly.

Live Vigilance Stats

Detection chance/s

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Bulls in thicket

Escapes

Close calls

How it works — many eyes vs. cover

Real nyala (Tragelaphus angasii) herds face a genuine trade-off that has nothing to do with steering toward food: every individual splits its time between grazing and scanning for predators, and the more animals in the group, the less scanning each one needs to do — yet the herd as a whole gets more likely to spot a predator, not less, because detection only needs one pair of eyes to succeed. This simulation rolls that per-individual detection chance every tick and combines it honestly rather than scripting an outcome.

Many-eyes / dilution effect: per-capita scan effort falls as herd size grows (division of vigilance labour), but combined detection probability = 1−(1−p)^N still climbs with N.
Woodland density is a genuine dual-edged trade: thicker cover shortens the sight lines the herd can scan (and also slows the leopard's own approach through it), while open glades give long sight lines but no concealment.
Sexual habitat segregation: only male nyala carry horns in real life. Here bulls (larger, horned) drift toward denser thicket for its forage and cover, tolerating the reduced visibility, while hornless ewes and calves hold the open glades where the herd's collective vigilance is sharpest — mirroring documented habitat-use asymmetry between the sexes.
Vigilance coordination models how efficiently the herd avoids redundant scanning; poor coordination wastes eyes watching the same directions.

grazing

Dense thicket Bull (thicket-leaning) Ewe / calf (glade-leaning) Leopard