diff --git a/data/json/monsters/mammal.json b/data/json/monsters/mammal.json
index b60b36a1b1c96..490c7e982f184 100644
--- a/data/json/monsters/mammal.json
+++ b/data/json/monsters/mammal.json
@@ -18,7 +18,7 @@
     "dodge": 2,
     "harvest": "mammal_fur",
     "special_attacks": [ [ "EAT_FOOD", 60 ] ],
-    "upgrades": { "age_grow": 42, "into": "mon_bear" }
+    "upgrades": { "age_grow": 480, "into": "mon_bear" }
   },
   {
     "id": "mon_bear",
@@ -52,7 +52,8 @@
     "placate_triggers": [ "MEAT" ],
     "death_function": [ "NORMAL" ],
     "harvest": "mammal_large_fur",
-    "reproduction": { "baby_monster": "mon_bear_cub", "baby_count": 1, "baby_timer": 13 },
+    "reproduction": { "baby_monster": "mon_bear_cub", "baby_count": 1, "baby_timer": 700 },
+    "//": "220 days gestation period, the mother and cubs remain together for 16-17 months.",
     "baby_flags": [ "SPRING" ],
     "special_attacks": [ [ "EAT_FOOD", 20 ] ],
     "flags": [ "SEES", "HEARS", "SMELLS", "ANIMAL", "PATH_AVOID_DANGER_1", "WARM", "BLEED", "BASHES", "ATTACKMON" ]
@@ -430,7 +431,7 @@
     "path_settings": { "max_dist": 10 },
     "fear_triggers": [ "SOUND", "PLAYER_CLOSE" ],
     "death_function": [ "NORMAL" ],
-    "upgrades": { "age_grow": 14, "into": "mon_deer" },
+    "upgrades": { "age_grow": 330, "into": "mon_deer" },
     "flags": [ "SEES", "HEARS", "SMELLS", "ANIMAL", "PATH_AVOID_DANGER_1", "WARM" ]
   },
   {
@@ -461,7 +462,8 @@
     "path_settings": { "max_dist": 10 },
     "fear_triggers": [ "SOUND", "PLAYER_CLOSE" ],
     "death_function": [ "NORMAL" ],
-    "reproduction": { "baby_monster": "mon_deer_fawn", "baby_count": 1, "baby_timer": 13 },
+    "reproduction": { "baby_monster": "mon_deer_fawn", "baby_count": 1, "baby_timer": 330 },
+    "//": " 201 days gestation period. The fawn will stay with its mother for approximately one year, suckling for three to four months.",
     "biosignature": { "biosig_item": "feces_manure", "biosig_timer": 12 },
     "baby_flags": [ "SPRING", "SUMMER" ],
     "special_attacks": [ [ "EAT_CROP", 60 ] ],
@@ -1637,7 +1639,7 @@
     "fear_triggers": [ "SOUND", "PLAYER_CLOSE" ],
     "placate_triggers": [ "MEAT" ],
     "death_function": [ "NORMAL" ],
-    "upgrades": { "age_grow": 20, "into": "mon_pig" },
+    "upgrades": { "age_grow": 38, "into": "mon_pig" },
     "biosignature": { "biosig_item": "feces_manure", "biosig_timer": 7 },
     "special_attacks": [ [ "EAT_FOOD", 40 ] ],
     "flags": [ "SEES", "HEARS", "SMELLS", "ANIMAL", "PATH_AVOID_DANGER_1", "WARM", "KEENNOSE", "BLEED" ]
@@ -1666,8 +1668,9 @@
     "melee_cut": 4,
     "dodge": 2,
     "harvest": "mammal_large_leather",
-    "reproduction": { "baby_monster": "mon_pig_piglet", "baby_count": 3, "baby_timer": 10 },
-    "baby_flags": [ "SPRING", "AUTUMN" ],
+    "reproduction": { "baby_monster": "mon_pig_piglet", "baby_count": 8, "baby_timer": 154 },
+    "//": "116 days gestation, 3-5 weeks until the piglets get weaned, 10-30 days of maturation",
+    "baby_flags": [ "SPRING", "SUMMER", "AUTUMN", "WINTER" ],
     "biosignature": { "biosig_item": "feces_manure", "biosig_timer": 2 },
     "path_settings": { "max_dist": 10 },
     "anger_triggers": [ "PLAYER_WEAK", "FRIEND_ATTACKED" ],
@@ -1816,7 +1819,8 @@
     "fear_triggers": [ "SOUND", "PLAYER_CLOSE", "FRIEND_ATTACKED" ],
     "placate_triggers": [ "PLAYER_WEAK" ],
     "death_function": [ "NORMAL" ],
-    "upgrades": { "age_grow": 20, "into": "mon_sheep" },
+    "upgrades": { "age_grow": 240, "into": "mon_sheep" },
+    "//": "Puberty reached in 6-9 months.",
     "biosignature": { "biosig_item": "feces_manure", "biosig_timer": 7 },
     "flags": [ "SEES", "HEARS", "SMELLS", "ANIMAL", "PATH_AVOID_DANGER_1", "WARM" ]
   },
@@ -1844,8 +1848,9 @@
     "starting_ammo": { "milk_raw": 2 },
     "anger_triggers": [  ],
     "harvest": "mammal_large_wool",
-    "reproduction": { "baby_monster": "mon_sheep_lamb", "baby_count": 1, "baby_timer": 20 },
-    "baby_flags": [ "SPRING", "SUMMER", "AUTUMN" ],
+    "reproduction": { "baby_monster": "mon_sheep_lamb", "baby_count": 1, "baby_timer": 275 },
+    "//": "Sheep are seasonal breeders. The natural sexual season is positioned so that lambs will be born in the spring when the weather is warmer and grass is available.",
+    "baby_flags": [ "SPRING" ],
     "biosignature": { "biosig_item": "feces_manure", "biosig_timer": 3 },
     "fear_triggers": [ "SOUND", "PLAYER_CLOSE", "FRIEND_ATTACKED" ],
     "placate_triggers": [ "PLAYER_WEAK" ],