diff --git a/src/mw_engine/natural_rules.clj b/src/mw_engine/natural_rules.clj
index ddbdad1..a1395f6 100644
--- a/src/mw_engine/natural_rules.clj
+++ b/src/mw_engine/natural_rules.clj
@@ -11,45 +11,45 @@
 
 ;; rules describing vegetation
 (def vegetation-rules
-  (list 
+  (list
     ;; Randomly, birds plant tree seeds into pasture.
     (fn [cell world] (cond (and (= (:state cell) :pasture)(< (rand 10) 1))(merge cell {:state :scrub})))
     ;; Scrub below the treeline grows gradually into forest, providing browsing pressure is not to high
-    (fn [cell world] 
-      (cond (and 
+    (fn [cell world]
+      (cond (and
               (= (:state cell) :scrub)
               ;; browsing limit really ought to vary with soil fertility, but...
               (< (+ (population cell :deer)(or (:sheep cell) 0)) 6)
-              (< (:altitude cell) treeline)) 
+              (< (:altitude cell) treeline))
         (merge cell {:state :scrub2})))
     (fn [cell world] (cond (= (:state cell) :scrub2) (merge cell {:state :forest})))
     ;; Forest on fertile land at low altitude grows to climax
-    (fn [cell world] 
-      (cond 
-        (and 
-          (= (:state cell) :forest) 
-          (> (:fertility cell) 10)) 
+    (fn [cell world]
+      (cond
+        (and
+          (= (:state cell) :forest)
+          (> (:fertility cell) 10))
         (merge cell {:state :climax})))
     ;; Climax forest occasionally catches fire (e.g. lightning strikes)
     (fn [cell world] (cond (and (= (:state cell) :climax)(< (rand lightning-probability) 1)) (merge cell {:state :fire})))
     ;; Climax forest neighbouring fires is likely to catch fire
     (fn [cell world]
-      (cond 
+      (cond
         (and (= (:state cell) :climax)
              (< (rand 3) 1)
              (not (empty? (get-neighbours-with-state world (:x cell) (:y cell) 1 :fire))))
         (merge cell {:state :fire})))
     ;; After fire we get waste
     (fn [cell world] (cond (= (:state cell) :fire) (merge cell {:state :waste})))
-    ;; And after waste we get pioneer species; if there's a woodland seed 
+    ;; And after waste we get pioneer species; if there's a woodland seed
     ;; source, it's going to be scrub, otherwise grassland.
     (fn [cell world]
       (cond
         (and (= (:state cell) :waste)
-             (not 
-               (empty? 
-                 (flatten 
-                   (list 
+             (not
+               (empty?
+                 (flatten
+                   (list
                      (get-neighbours-with-state world (:x cell) (:y cell) 1 :scrub2)
                      (get-neighbours-with-state world (:x cell) (:y cell) 1 :forest)
                      (get-neighbours-with-state world (:x cell) (:y cell) 1 :climax))))))
@@ -72,7 +72,7 @@
                  (< (rand 50) 1)
                  (= (population cell :deer) 0))
         (merge cell {:deer 2})))
-    ;; if there are too many deer for the fertility of the area to sustain, 
+    ;; if there are too many deer for the fertility of the area to sustain,
     ;; some die or move on.
     (fn [cell world]
       (cond (> (* (population cell :deer) 10) (:fertility cell))
@@ -86,16 +86,16 @@
           (merge cell {:deer (int (/ n 2))}))))
     ;; deer breed.
     (fn [cell world]
-      (cond 
+      (cond
         (>= (population cell :deer) 2)
         (merge cell {:deer (int (* (:deer cell) 4))})))
     ;; wolves arrive occasionally at the edge of the map.
-;;    (fn [cell world]
-;;      (cond (and (< (count (get-neighbours world cell)) 8)
-;;                 (< (rand 50) 1)
-;;                 (= (population cell :wolves) 0))
-;;        (merge cell {:wolves 2})))
-    ;; if there are not enough deer to sustain the population of wolves, 
+    (fn [cell world]
+      (cond (and (< (count (get-neighbours world cell)) 8)
+                 (< (rand 50) 1)
+                 (= (population cell :wolves) 0))
+        (merge cell {:wolves 2})))
+    ;; if there are not enough deer to sustain the population of wolves,
     ;; some wolves die or move on.
     (fn [cell world]
       (cond (> (population cell :wolves) (population cell :deer))
@@ -109,7 +109,7 @@
           (merge cell {:wolves 2}))))
     ;; wolves breed.
     (fn [cell world]
-      (cond 
+      (cond
         (>= (population cell :wolves) 2)
         (merge cell {:wolves (int (* (:wolves cell) 2))})))
     ;; wolves eat deer