A survival game · real odds from the field
You are a vampire bat.
You are a young bat, still learning to hunt, and you feed on the blood of sleeping cattle. Three nights without a meal will kill you — and you strike out far more often than the adults roosting around you. When your luck fails, only your friends can save you: vampire bats share blood with the partners who have groomed and fed them before. Fifteen nights stand between you and the wet season. The last of them are storms. Build the bonds that will carry you through.
Longest-lived bats
| # | Player | Species | Score | Survived | When |
|---|---|---|---|---|---|
| Loading scores… | |||||
How the odds work
Sourced numbers (see the Learn more page for full citations): adult bats fail to feed on ~7% of nights, young bats on up to a third of theirs, and you start young — your hidden hunting skill is drawn around a 28% fail rate and improves with every successful night, the way real juveniles learn. ~70 fasting hours is fatal (≈3 nights of reserve). When your reserve hits zero, each roost-mate who fed that night rescues you with P = 0.02 + 0.60 × bond — real rescues track prior grooming and giving, not kinship. Donations are graded (a sip to a full crop) and build bonds in proportion; grooming escalates into sharing; grooming also keeps the mites off (below 0.5 hygiene they move in and drain −0.5 🩸 a night). Bright moonlight suppresses vampire bat foraging (Crespo et al. 1972) — on bright nights every bat's odds worsen.
Plausible, for play (invented for the game, flagged so you know): the exact size of the moonlight penalty (+15%), storm and squall modifiers (+15–18% fail, misses burn 1.5 🩸), the learning rate (fail ×0.93 per success), bond decay (−0.02/night), roost-mates' hidden personalities (big-hearted, tight-furred, far-ranger, thin), and roost-mates rescuing each other through their own friendships. Roost-mates can genuinely starve: a begging bat that no one feeds — including you — dies, and its friendships die with it.
Score is a fitness ledger: nights survived, donations (scaled by size and need), lives
saved, grooming given, and your final bond portfolio. Death keeps the ledger you earned.
Balance targets and results are recorded in sim/batsim2.py (20,000-run Monte
Carlo per strategy).