Clock 06:00Tide 0 m Dry rock 0 sealsHauled 0Foraging 0Rafting 0Fat 0 %Boat noise -FPS 0

Drag to orbit, wheel or pinch to zoom. Seals haul out on rock shelves that the falling tide uncovers, swim to the colour-coded fish hotspots (red = densest, model data, not telemetry) and dive. Dashed lines are the tracks of four tagged seals.

Harbour Seal Haul-Out Lab

Tide opens and floods the rocks; hunger, boat noise and heat decide who is on them. All numbers are model values, not data from a real colony.

Sea and shore

Fish and diving

Disturbance

Live readouts

Tide and dry rock

Hauled out and in the water

Population projection (stage matrix)

Experiments

Each button runs 4 simulated days headless for several values (same seed) and reports the colony's behaviour.

Independent numerical checks

Controls

Drag / one finger: orbit; wheel / pinch: zoom. Views jump to the split-level frame, a rocks close-up, an underwater frame and a map.
Sliders act at once, except "Colony size", which restarts the colony. "Time scale" is simulated minutes per real second; one tidal cycle takes 12.4 simulated hours.
The fish map and the dashed tracks can be hidden with the Fish map button.

The science

Tide. Two constituents: h(t) = h₀ + A_M2 cos(2πt/12.42 h − φ₁) + A_S2 cos(2πt/12.00 h − φ₂); their beat gives spring and neap tides every 14.77 days. A rock shelf is dry when its height exceeds h(t) + 0.12 m; capacity = dry shelves, one seal per 2.5 m².

Haul-out. Tendency to be hauled out: P = 1/(1 + e^{−3 (h_thr − h)}) · f_temp · f_sun · f_noise with a heat penalty above 25 °C and a strong penalty for 30 min after a noise flush. Hungry seals leave earlier.

Dive and energy. Metabolic power from Kleiber: P = 3.4 m^0.75 W, scaled by activity (2.5 in the field, ×dive multiplier while diving). Aerobic dive limit ADL = m c_O₂ E_O₂ / (k P), with c_O₂ = 45 mL O₂/kg and 20.1 kJ per litre (a model value of the right order for phocids). Fish intake follows Holling's type II response f(ρ) = a ρ / (1 + a h_t ρ / m_f) (a = 0.02 m³/s, h_t = 20 s, fish mass 50 g). Fish density on a 64×64 grid: ∂ρ/∂t = D∇²ρ − ∇·(vρ) + rρ(1 − ρ/K) − predation, conservative upwind + diffusion scheme, no-flux walls.

Noise. SPL(r) = SL − 20 log₁₀ r − α r (spherical spreading plus absorption); a flush happens with probability logistic((SPL − 120 dB)/3) when a boat passes. The 120 dB re 1 µPa threshold is a model value.

Population. A three-stage (pup, juvenile, adult) matrix; pup survival is 0.75 × nursing factor (share of time pups spend hauled with the colony) × noise factor. The projection assumes every future year looks like the recent days.

Honest limits. Model seals are agents with simple rules, not individual behaviour data; the heat map is simulated fish, not telemetry; no predators are shown (risk would only be a hazard rate); one species, mean parameters, no disease, a 2-D fish map with a fixed 12 m column. Assets built with Blender; scene by Three.js.