Choose an animal model by biological question

High-throughput mechanistic models

Short generation times and strong genetic toolkits support screens, pathway dissection, interaction mapping, and rapid replication.

• Strengths: scale, genetic precision, conserved cell biology, and economical lifespan studies.
• Limitations: major differences in organs, immunity, metabolism, pharmacology, and causes of death.
• Best practice: reproduce the mechanism in a second organism and test the mammalian orthologue or pathway.

Short-lived vertebrate models

Vertebrate tissues and experimental accessibility can bridge invertebrate discovery and mammalian physiology.

• Strengths: imaging, regeneration, genetics, organ-level phenotypes, and relatively rapid ageing studies.
• Limitations: strain, temperature, water conditions, reproductive strategy, and teleost-specific genome duplication.
• Best practice: resolve paralogues and match husbandry, sex, tissue, and life stage across experiments.

Mammalian intervention models

Rodents support controlled genetics, longitudinal phenotyping, tissue collection, pharmacology, pathology, and survival studies.

• Strengths: standardized resources, engineered alleles, defined populations, and deep physiological assays.
• Limitations: background-specific effects, husbandry dependence, compressed timescale, and incomplete human disease fidelity.
• Best practice: use justified genetic diversity, both sexes where relevant, independent cohorts, and functional endpoints.

Naturally long-lived and non-traditional species

Species with unusual longevity, disease resistance, regeneration, or ecology can reveal biological solutions not apparent in standard laboratory models.

• Strengths: naturally evolved phenotypes and large contrasts in life history.
• Limitations: small samples, opportunistic tissues, variable age estimates, limited reagents, and conservation constraints.
• Best practice: avoid anecdotal exceptionalism; use phylogenetically informed designs and functional validation.

GenAge model organisms

Curated genes associated with ageing or longevity in model organisms, with evidence linked to the underlying studies.

• Search by gene or organism and inspect the exact manipulation and phenotype.
• Use provided human-homologue information as a starting point, then confirm current orthology independently.
• Separate lifespan modification from other ageing phenotypes.

AnAge

Curated animal longevity and life-history information for comparative model selection and hypothesis framing.

• Inspect record confidence, observation notes, captivity, body mass, and taxonomy.
• Do not treat a species record as the expected survival of a laboratory cohort.
• Use lifespan contrasts with ecological and phylogenetic covariates.

International Mouse Phenotyping Consortium

A standardized, open catalogue of phenotypes generated from mouse knockout lines and matched controls.

• Inspect allele, background, zygosity, sex, procedure, age, centre, and data-release version.
• Use late-adult and histopathology collections where they match the ageing question.
• A phenotype association is not automatically a lifespan effect; locate the measured endpoint.

Mouse Phenome Database

A standardized collection of measured data from laboratory mouse strains and populations, including ageing, diet, drug, disease, genotype, and expression studies.

• Compare strains only within compatible projects, protocols, ages, sexes, and environments.
• Use project metadata and individual-level measurements where available.
• Track whether a study uses inbred, hybrid, Collaborative Cross, Diversity Outbred, or another population.

NIA Interventions Testing Program

A multi-site platform for evaluating candidate interventions in genetically heterogeneous mice using coordinated protocols.

• Review compound, dose, start age, sex, site, cohort, survival, pathology, and health measures.
• Include null and adverse outcomes when evaluating reproducibility.
• Do not generalize a protocol-specific mouse result directly to humans.

NIA Aged Rodent Colonies

Barrier-raised, health-monitored aged mouse and rat resources for eligible research focused on ageing and age-related disease.

• Check current strains, ages, sexes, availability, eligibility, and ordering constraints.
• Document source colony, health report, shipment, acclimation, and experimental housing.
• Use the current colony information rather than assuming a strain remains available.

Species, strain, stock, and allele

• Accepted scientific name and taxonomic identifier.
• Full strain or stock nomenclature, substrain, breeding design, and genetic diversity.
• Allele, zygosity, construct, driver, reporter, induction schedule, and off-target assessment.
• Genetic quality control and drift-monitoring strategy.

Sex, age, life stage, and tissue

• Sex, reproductive state, exact or bounded age, and developmental or ageing stage.
• Tissue, anatomical region, cell identity, collection time, and circadian context.
• Baseline function, disease status, prior treatment, and exclusion criteria.
• Whether the comparison is cross-sectional, longitudinal, or terminal.

Husbandry and exposure

• Facility, barrier, pathogen status, room, cage density, bedding, enrichment, temperature, and light cycle.
• Diet formulation, feeding schedule, water, microbiome considerations, and co-housing.
• Handling, transport, acclimation, intervention vehicle, dose, route, and exposure confirmation.
• Site effects and protocol deviations.

Endpoint and analysis population

• Primary and secondary endpoints, event definitions, time origin, and measurement schedule.
• Randomization unit, blocking, allocation concealment, blinding, sample-size rationale, and exclusions.
• Censoring, missingness, competing risks, repeated measures, batch, and multiplicity plan.
• Code, protocol, ontology, data-release version, and provenance.

Reduce bias and wasted experiments

• Use systematic evidence review, a prespecified protocol, appropriate controls, and a justified sample size.
• Randomize and blind wherever feasible; define exclusions before unblinding.
• Report all prespecified endpoints, null findings, adverse events, deviations, and attrition.
• Share protocols, code, metadata, and reusable data under applicable consent and license terms.

Apply the 3Rs throughout the programme

• Replacement: use cells, organoids, computation, or lower-complexity models when they can answer the question.
• Reduction: extract multiple compatible endpoints and coordinate tissues without compromising statistical validity.
• Refinement: minimize pain and distress, use appropriate monitoring, and define humane endpoints.
• Obtain institutional and regulatory approval appropriate to the species, site, and procedure.