Life History of Marine Mammals

A vocabulary-style set of flashcards covering key terms and concepts from the Life History of Marine Mammals lecture notes.

Life history

Events from birth to death and the allocation of resources among growth, reproduction, and survival to maximize fitness.

Life history analysis

Explains how organisms schedule resource allocation over time to optimize fitness.

Cetaceans

Whales, dolphins, and porpoises; marine mammals studied under life-history strategies.

Longitudinal studies

Following known individuals through their lifetimes; rare but valuable for variability in reproduction and survival.

Cross‑sectional studies

Data from dead animals or snapshots (e.g., from strandings) used to infer age, maturity, and morphology.

Remote sampling

Techniques to study reproduction and movement patterns from a distance (e.g., noninvasive sampling).

Molecular markers

Biomarkers derived from skin or blubber used to assess genetics, health, and exposure.

Hormones

Biochemical indicators of reproductive status and other physiological processes.

Stable isotopes

Isotopic signatures used to infer foraging ecology and dietary patterns.

Satellite/VHF tags

Tracking devices used to study movement, physiology, and predator–prey dynamics.

Life history strategies

Diverse strategies in how species allocate energy to growth, reproduction, and survival.

Odontocetes

Toothed whales; highly diverse in size and habitat.

Mysticetes

Baleen whales; large, long-lived with distinct migratory and feeding patterns.

Well-studied species

Humpback whale, Bottlenose dolphin, Orca; studied since the 1970s for life-history traits.

Lifespan (baleen vs toothed)

Baleen whales: ~60 years (some >100); Bowhead may approach ~200; Toothed whales ~20 years; some porpoises ~100 years.

Birth characteristics

Usually a single large, precocial calf; multiple fetuses are rare; gestation about a year (baleen 10–12 months; toothed 10–17 months).

Sexual dimorphism in growth

Growth patterns differ by sex; growth rates and final size vary with species and sex.

Neonates relative size

Neonates are large relative to adults: baleen calves ~29% of adult female size; toothed calves ~40–48%.

Lactation duration

Baleen whales ~6 months; toothed whales often >1 year.

Gestation in baleen vs toothed

Baleen gestation ~11 months; toothed gestation ~10–15/17 months.

Male growth patterns in toothed whales

Males often show pronounced size differences (e.g., sperm whales show strong dimorphism).

Cycle patterns in baleen whales

Minimum reproductive cycle of ~2 years (gestation + lactation + rest); some species have 3–4 year cycles.

Migration and reproduction

Breeding cycles often synced with long-distance migrations; potential benefits include neonate survival and reduced thermoregulatory demands.

Toothed whale calving intervals

Smaller delphinids ~2–3 years; larger delphinids >3 years; gestation ~11–12 months; lactation ~1–2 years (smaller) or 2–3+ years (larger).

Breeding synchrony

Temperate waters show peaks in synchrony with productivity; tropical waters may have year-round or diffuse breeding.

Age of maturity in baleen whales

Varies by species; examples: Humpbacks ~4 years; Fin & Bryde’s ~10 years; Bowhead ~25 years.

Age of maturity in toothed whales

Varies widely; harbor porpoise ~3 years; many species ~10+ years; some live to 40+ years.

Reproductive success variability

Varies with age and life stage; peaks after maturity and often declines with age; social structure can enhance offspring survival.

Post-reproductive females

Some toothed whales have post-reproductive females; evidence in baleen whales is unclear.

Male life-history information

Fewer studies; males often invest energy in reproduction; dimorphism can affect maturation and lifespan patterns.

Life history and demography

Life history strategy underpins population demography; age-specific reproduction and survival are needed to estimate growth rates.

Density dependence

Resource availability affects life-history traits (e.g., age of maturity) and reproduction across populations.

Sirenians

Manatees and dugongs; long-term life-history studies and aging methods.

Florida manatees life-history study

40+ year study; Manatee Individual Photo-Identification System used for monitoring.

Manatee longevity

Estimated lifespans up to ~60 years; Snooty the manatee lived to 69 in captivity.

Dugong longevity

Oldest female ~73 years; oldest male ~35 years; tusk growth used for aging.

Reproductive maturity in Florida manatees

Females ~2.5–6 years; males ~2.5–11 years.

Reproductive maturity in dugongs

Females ~10–17 years; males ~9–16 years.

Birth size in manatees and dugongs

Birth length around 120 cm; birth weight 30–50 kg in manatees; 25–35 kg in dugongs.

Max length/weight

Manatees up to about 300 cm long; 200–600 kg; females larger than males.

Gestation and interbirth in manatees and dugongs

Gestation ~12 months; interbirth interval ~2.5 years in manatees; ~2.7–5.8 years in dugongs.

Pinnipeds life history features

High annual survival (20–40 year lifespans); maturity around 3–7 years; one calf per cycle; semi-aquatic constraints.

Precocial offspring

Young are relatively mature and mobile soon after birth; can forage independently soon after birth in pinnipeds.

Body size and life history

No simple, universal link between body size and life-history traits across species; variation exists within species.

Capital breeding

Rely on endogenous reserves (blubber) to sustain reproduction; notable in Northern Elephant Seals.

Income breeding

Use foraging to support lactation; notable in Antarctic fur seals.

Capital and income breeding continuum

Breeding strategies range between capital and income, influenced by intrinsic and extrinsic factors.

Costs and benefits of breeding

Reproduction increases offspring fitness but can raise parental mortality risk due to energy investment.

Male reproductive strategy and longevity

Males may invest heavily in reproduction and often have different maturation timelines and life spans compared to females.

Next week topics (overview)

Acoustics, sound production; orca biology; acoustics and hearing.