Methodology

How selection works

• A batch draws between 1 and 50 records. Each eligible record has an equal chance of being drawn.
• A batch never contains the same animal twice. Selection uses a partial Fisher-Yates shuffle over the eligible records, not a random sort comparator, which would be biased.
• Uniform means uniform across the catalog, not across real animal populations. A blue whale and a garden snail are equally likely.
• Asking for more animals than a group holds returns the whole group and tells you that it did.

The no-repeat setting

With no repeats on, the page remembers which animals it has already shown and skips them in later batches. When no unseen animals are left it stops and says so. It never quietly starts repeating, so a batch handed out one animal per child cannot reissue an animal from an earlier batch. Select Reset to start a fresh cycle.

That memory lives in the page only. It is not saved to your device or sent anywhere, so a reload clears it.

Where the data comes from

The six group labels are the categories commonly used to sort animals in school, not six formal groups in biology. Mammals, birds and amphibians are formal groups. Fish and invertebrates are not: they are convenient bundles, and the groups guide explains where each label stops working. The labels were checked against Integrated Taxonomic Information System (ITIS) on 2026-09-19.

Common names are everyday English names chosen by the maintainer. They are not species identifications, and no scientific name is shown, because a common name often covers several species. “Glass frog” names a family of many species, not one animal.

This is the honest limit of catalog v1.2.0: the checking was done over the catalog as a whole, at the level of these six labels. No animal was researched individually, and linking a taxonomic database is not a claim that each record was verified against it. If you need species-accurate data, use Integrated Taxonomic Information System (ITIS) directly.

Photographs

12 of the 449 animals carry a photograph. The rest show a coloured tile for their group, so a batch never renders as a few pictures beside a row of holes. Switch to With photos to draw only from the ones that have an image.

Every photograph comes from Wikimedia Commons under a licence that permits reuse and change. For each file we record the creator, the licence, the original file page, what we changed, a checksum of the served file and the date it was retrieved.

All of that is public on the photo credits page. Licences are reproduced as they read on the retrieval date, which is a record of what was found rather than legal advice. Check the source link before reusing any photograph yourself.

What the catalog leaves out

• Extinct animals, including dinosaurs. Every record is a living animal.
• Invented and mythical animals.
• Dog and cat breeds. A breed is not a separate animal, and mixing them in would skew the batches.
• Two names for one animal. The catalog holds either “orca” or “killer whale”, never both, so one animal cannot appear twice in a batch under two names.
• A photograph for every animal. Only some records carry one, and the photo section below says how many and where they come from.

Changes to the catalog

The version number rises whenever records change. Adding or removing animals changes the minor number; correcting a name or a group label changes the patch number. Record IDs are never reused for a different animal.