Methodology and sources

How we pick species

The site covers 45 species: nine in each of five groups. Each species was chosen because it shows one clear idea well, such as venom, regeneration or temperature-dependent sex. We aim for a mix of well-known and lesser-known animals from different parts of the world.

Where facts come from

Source	What we use it for
IUCN Red List	Conservation category, read through GBIF (see below).
GBIF, the Global Biodiversity Information Facility	Open data service that republishes the IUCN Red List categories. We read the category here.
AmphibiaWeb	Amphibian biology, range and taxonomy.
The Reptile Database	Reptile names, range and taxonomy.
Smithsonian	General biology and conservation background.
Natural history museums and universities	Explanations of traits, research summaries and field findings.

Each article lists the exact pages we used. Reference sites are living databases, so we also record the date we opened each one.

How we check conservation status

The IUCN Red List website does not allow automated lookups, so we read each category from the IUCN data that GBIF distributes, through GBIF's open service. The day we read it is printed next to it. Two limits you should know: GBIF's copy can trail the IUCN website by some months, and it does not carry the year of the assessment, so we never print a year. If GBIF has no IUCN record for a species, the article says the category is to be confirmed instead of guessing. Categories can go up or down when a species is reassessed, so treat the date as part of the information, and check the IUCN Red List for anything that matters.

How the game clues are written

• Each species has at least six clues: two easy, two medium and two hard.
• Easy clues describe habitat, size or diet. Medium clues describe adaptations and behavior. Hard clues separate animals that look alike.
• A clue never contains the animal's common or scientific name. The site refuses to build if one does.
• Clues are short, up to 14 words, so they fit on a card. Short means simplified: a clue is a hint, not a full description.

Limits

Species Match is an educational game and its clues simplify. Conservation categories change. Your progress is stored only on the device you play on. These limits are repeated on the game page.

Reading level and tone

We write for curious readers aged about 12 and up, in plain English, with the occasional joke. We define technical terms the first time they appear.